Minor fixes on MEC028 robot tests.

MEC028/WAI/AP_INFO/WaiApInfo.robot

@@ -63,7 +63,7 @@ Retrieve the access point information
     Should Be True    ${PIC_MEC_SYSTEM} == 1
     Should Be True    ${PIC_SERVICES} == 1
     Set Headers    {"Accept":"application/json"}
-    Set Headers    {"Content-Type":"application/json"}
+    Set Headers    {"Content-Type":"*/*"}
     Set Headers    {"Authorization":"${TOKEN}"}
     GET     ${apiRoot}/${apiName}/${apiVersion}/queries/ap/ap_information
     ${output}=    Output    response
@@ -74,7 +74,7 @@ Retrieve the access point information using filters
     Should Be True    ${PIC_MEC_SYSTEM} == 1
     Should Be True    ${PIC_SERVICES} == 1
     Set Headers    {"Accept":"application/json"}
-    Set Headers    {"Content-Type":"application/json"}
+    Set Headers    {"Content-Type":"*/*"}
     Set Headers    {"Authorization":"${TOKEN}"}
     GET     ${apiRoot}/${apiName}/${apiVersion}/queries/ap/ap_information?filter=${filter}
     ${output}=    Output    response

MEC028/WAI/EXT_SUB/ExistingSubscription.robot

@@ -87,7 +87,7 @@ Retrieve existing subscription information
     Should Be True    ${PIC_MEC_SYSTEM} == 1
     Should Be True    ${PIC_SERVICES} == 1
     Set Headers    {"Accept":"application/json"}
-    Set Headers    {"Content-Type":"application/json"}
+    Set Headers    {"Content-Type":"*/*"}
     Set Headers    {"Authorization":"${TOKEN}"}
     GET     ${apiRoot}/${apiName}/${apiVersion}/subscriptions/${SUB_ID}
     ${output}=    Output    response
@@ -99,7 +99,7 @@ Modify existing subscription information
     Should Be True    ${PIC_MEC_SYSTEM} == 1
     Should Be True    ${PIC_SERVICES} == 1
     Set Headers    {"Accept":"application/json"}
-    Set Headers    {"Content-Type":"application/json"}
+    Set Headers    {"Content-Type":"*/*"}
     Set Headers    {"Authorization":"${TOKEN}"}
     ${path}    Catenate    SEPARATOR=      jsons/     ${content}
     ${body}    Get File    ${path}
@@ -113,7 +113,7 @@ Remove existing subscription information
     Should Be True    ${PIC_MEC_SYSTEM} == 1
     Should Be True    ${PIC_SERVICES} == 1
     Set Headers    {"Accept":"application/json"}
-    Set Headers    {"Content-Type":"application/json"}
+    Set Headers    {"Content-Type":"*/*"}
     Set Headers    {"Authorization":"${TOKEN}"}
     DELETE     ${apiRoot}/${apiName}/${apiVersion}/subscriptions/${SUB_ID}
     ${output}=    Output    response

MEC028/WAI/STA_INFO/WaiStaInfo.robot

@@ -63,7 +63,7 @@ Retrieve the station information
     Should Be True    ${PIC_MEC_SYSTEM} == 1
     Should Be True    ${PIC_SERVICES} == 1
     Set Headers    {"Accept":"application/json"}
-    Set Headers    {"Content-Type":"application/json"}
+    Set Headers    {"Content-Type":"*/*"}
     Set Headers    {"Authorization":"${TOKEN}"}
     GET     ${apiRoot}/${apiName}/${apiVersion}/queries/sta/sta_information
     ${output}=    Output    response
@@ -74,7 +74,7 @@ Retrieve the station information using filters
     Should Be True    ${PIC_MEC_SYSTEM} == 1
     Should Be True    ${PIC_SERVICES} == 1
     Set Headers    {"Accept":"application/json"}
-    Set Headers    {"Content-Type":"application/json"}
+    Set Headers    {"Content-Type":"*/*"}
     Set Headers    {"Authorization":"${TOKEN}"}
     GET     ${apiRoot}/${apiName}/${apiVersion}/queries/sta/sta_information?filter=${filter}
     ${output}=    Output    response

MEC028/WAI/SUB/WaiSubscription.robot

@@ -123,7 +123,7 @@ Retrieve the subscription information
     Should Be True    ${PIC_MEC_SYSTEM} == 1
     Should Be True    ${PIC_SERVICES} == 1
     #Set Headers    {"Accept":"application/json"}
-    Set Headers    {"Content-Type":"application/json"}
+    Set Headers    {"Content-Type":"*/*"}
     Set Headers    {"Authorization":"${TOKEN}"}
     GET     ${apiRoot}/${apiName}/${apiVersion}/subscriptions?subscription_type=${subscription_type}
     ${output}=    Output    response
@@ -133,7 +133,7 @@ Retrieve the subscription information using wrong endpoint
     Should Be True    ${PIC_MEC_SYSTEM} == 1
     Should Be True    ${PIC_SERVICES} == 1
     #Set Headers    {"Accept":"application/json"}
-    Set Headers    {"Content-Type":"application/json"}
+    Set Headers    {"Content-Type":"*/*"}
     Set Headers    {"Authorization":"${TOKEN}"}
     GET     ${apiRoot}/${apiName}/${apiVersion}/subscriptions_INVALID_URI
     ${output}=    Output    response