sasl_sspi: Corrected some of the GSSAPI security message error codes

Corrected a number of the error codes that can be returned from the
Curl_sasl_create_gssapi_security_message() function when things go
wrong.

It makes more sense to return CURLE_BAD_CONTENT_ENCODING when the
inbound security challenge can't be decoded correctly or doesn't
contain the KERB_WRAP_NO_ENCRYPT flag and CURLE_OUT_OF_MEMORY when
EncryptMessage() fails. Unfortunately the previous error code of
CURLE_RECV_ERROR was a copy and paste mistakes on my part and should
have been correct in commit 4b491c67 :(