mgw: Support receiving uppercase connection mode

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: I4da93dfc69b5585a197a7e201a1afb72c2f97030
diff --git a/tests/mgcp/mgcp_test.c b/tests/mgcp/mgcp_test.c
index c67b9d5..5a14bdf 100644
--- a/tests/mgcp/mgcp_test.c
+++ b/tests/mgcp/mgcp_test.c
@@ -165,7 +165,7 @@
 
 #define MDCX4_PT1 \
 	"MDCX 18983217 1@mgw MGCP 1.0\r\n" \
-	"M: sendrecv\r" \
+	"M: SENDRECV\r" \
 	"C: 2\r\n" \
 	"I: %s\r\n" \
 	"L: p:20-40, a:AMR, nt:IN\r\n" \