vty: Rename 'mgcp-through-msc-ipa' command to 'use-msc-ipa-for-mgcp'

Currently the 'mgcp' command fails in the 'config-nat' node, because
it get confused with 'mgcp-through-msc-ipa' which is executed
instead because of the prefix based command selection. Thus the
latter command is renamed by this patch to avoid the common prefix.

The workaround in the test suite is removed.
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c b/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c
index 9eab574..72a6801 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat_vty.c
@@ -152,7 +152,7 @@
 	llist_for_each_entry(pgroup, &_nat->paging_groups, entry)
 		write_pgroup_lst(vty, pgroup);
 	if (_nat->mgcp_ipa)
-		vty_out(vty, " mgcp-through-msc-ipa%s", VTY_NEWLINE);
+		vty_out(vty, " use-msc-ipa-for-mgcp%s", VTY_NEWLINE);
 
 	return CMD_SUCCESS;
 }
@@ -754,9 +754,9 @@
 	return CMD_SUCCESS;
 }
 
-DEFUN(cfg_nat_mgcp_ipa,
-      cfg_nat_mgcp_ipa_cmd,
-      "mgcp-through-msc-ipa",
+DEFUN(cfg_nat_use_ipa_for_mgcp,
+      cfg_nat_use_ipa_for_mgcp_cmd,
+      "use-msc-ipa-for-mgcp",
       "This needs to be set at start. Handle MGCP messages through "
       "the IPA protocol and not through the UDP socket.\n")
 {
@@ -1209,7 +1209,7 @@
 	install_element(NAT_NODE, &cfg_nat_ussd_query_cmd);
 	install_element(NAT_NODE, &cfg_nat_ussd_token_cmd);
 	install_element(NAT_NODE, &cfg_nat_ussd_local_cmd);
-	install_element(NAT_NODE, &cfg_nat_mgcp_ipa_cmd);
+	install_element(NAT_NODE, &cfg_nat_use_ipa_for_mgcp_cmd);
 
 	/* access-list */
 	install_element(NAT_NODE, &cfg_lst_imsi_allow_cmd);