patch 8.0.1079: memory leak when remote_foreground() fails

Problem:    Memory leak when remote_foreground() fails.
Solution:   Free the error message.
diff --git a/src/if_xcmdsrv.c b/src/if_xcmdsrv.c
index 4c3c012..2d87e30 100644
--- a/src/if_xcmdsrv.c
+++ b/src/if_xcmdsrv.c
@@ -420,6 +420,7 @@
 	    {
 		LookupName(dpy, loosename ? loosename : name,
 			   /*DELETE=*/TRUE, NULL);
+		vim_free(loosename);
 		continue;
 	    }
 	}