mgcp: make domain name configurable

At the moment the MGW has a fixed domain name string that is not even
checked properly.

- Make domain name configurable, use the current "mgw" string as
  defualt to maintain compatibility

- Check the domain name with each request. If the endpoint contains
  an unexpected domain name, the request must be rejected.

Change-Id: Ia91ac428ba83ac1f9b52a0ec8dbf00ef7876da9e
diff --git a/tests/mgcp/mgcp_test.c b/tests/mgcp/mgcp_test.c
index 46fd69b..467cb6c 100644
--- a/tests/mgcp/mgcp_test.c
+++ b/tests/mgcp/mgcp_test.c
@@ -66,18 +66,18 @@
 	OSMO_ASSERT(counter == EXPECTED_NUMBER_OF_LINES);
 }
 
-#define AUEP1	"AUEP 158663169 ds/e1-1/2@172.16.6.66 MGCP 1.0\r\n"
+#define AUEP1	"AUEP 158663169 ds/e1-1/2@mgw MGCP 1.0\r\n"
 #define AUEP1_RET "200 158663169 OK\r\n"
-#define AUEP2	"AUEP 18983213 ds/e1-2/1@172.16.6.66 MGCP 1.0\r\n"
+#define AUEP2	"AUEP 18983213 ds/e1-2/1@mgw MGCP 1.0\r\n"
 #define AUEP2_RET "500 18983213 FAIL\r\n"
 #define EMPTY	"\r\n"
 #define EMPTY_RET NULL
 #define SHORT	"CRCX \r\n"
 #define SHORT_RET "510 000000 FAIL\r\n"
 
-#define MDCX_WRONG_EP "MDCX 18983213 ds/e1-3/1@172.16.6.66 MGCP 1.0\r\n"
+#define MDCX_WRONG_EP "MDCX 18983213 ds/e1-3/1@mgw MGCP 1.0\r\n"
 #define MDCX_ERR_RET "500 18983213 FAIL\r\n"
-#define MDCX_UNALLOCATED "MDCX 18983214 ds/e1-1/2@172.16.6.66 MGCP 1.0\r\n"
+#define MDCX_UNALLOCATED "MDCX 18983214 ds/e1-1/2@mgw MGCP 1.0\r\n"
 #define MDCX_RET "400 18983214 FAIL\r\n"
 
 #define MDCX3 \