mgcp-client: Rearrange internal backpointers

Let's properly store backpointers so that it is easy to access all
relation chain (pool<->pool_member<->mgcp_client).

Related: SYS#5987
Change-Id: I5ec2465075da2e3c8eabca9df60681620a7db499
diff --git a/src/libosmo-mgcp-client/mgcp_client_vty.c b/src/libosmo-mgcp-client/mgcp_client_vty.c
index 81f8f3e..a823b0c 100644
--- a/src/libosmo-mgcp-client/mgcp_client_vty.c
+++ b/src/libosmo-mgcp-client/mgcp_client_vty.c
@@ -401,7 +401,7 @@
 		return CMD_WARNING;
 	}
 
-	if (mgcp_client_pool_member_reinit_client(pool_member, global_mgcp_client_pool) < 0) {
+	if (mgcp_client_pool_member_reinit_client(pool_member) < 0) {
 		LOGP(DLMGCP, LOGL_ERROR, "(manual) MGW %s connect failed at (%s:%u)\n",
 		     mgcp_client_pool_member_name(pool_member), pool_member->conf.remote_addr,
 		     pool_member->conf.remote_port);