[mgcp] Possible memleak fix for the allowed reallocation case

When allowing to reallocate an allocated endpoint we will need
to free it first. When freeing we will free the call id and other
ids that we would have leaked otherwise.
diff --git a/openbsc/src/mgcp/mgcp_protocol.c b/openbsc/src/mgcp/mgcp_protocol.c
index 6d5713c..d82bd68 100644
--- a/openbsc/src/mgcp/mgcp_protocol.c
+++ b/openbsc/src/mgcp/mgcp_protocol.c
@@ -389,6 +389,7 @@
 		if (cfg->force_realloc) {
 			LOGP(DMGCP, LOGL_NOTICE, "Endpoint 0x%x already allocated. Forcing realloc.\n",
 			    ENDPOINT_NUMBER(endp));
+			mgcp_free_endp(endp);
 		} else {
 			LOGP(DMGCP, LOGL_ERROR, "Endpoint is already used. 0x%x\n",
 			     ENDPOINT_NUMBER(endp));