SRV/APPSAQ/PlatAppServices.robot TC_MEC_SRV_APPSAQ_002_OK better set service_id as global variable, so the test suite can run together

$SERVICE_ID would be called in below test cases, so it should better be set as global variable and pass to below test cases, so that the test suite can run in a row. a change suggestrion would be:

[Tags] PIC_MEC_PLAT PIC_SERVICES Create new service ServiceInfo ${APP_INSTANCE_ID} Create new service ServiceInfo ${APP_INSTANCE_ID} Check HTTP Response Status Code Is 201 Check HTTP Response Status Code Is 201 Check HTTP Response Body Json Schema Is ServiceInfo Check HTTP Response Body Json Schema Is ServiceInfo Check HTTP Response Header Contains Location Check HTTP Response Header Contains Location Set Global Variable ${SERVICE_ID}