mgcp-cli: Support lowercase header parameters

MGCP RFC3435 (https://tools.ietf.org/html/rfc3435) states almost all
text has to be handled in a case-insensitive way, except SDP parts.

Related: OS#4001
Change-Id: I4f7b07b77c2946e9cd6f0eeca00011bd905126dd
1 file changed