Bug#36018640 Test UnresolvedHosts2 passes but ndbd aborts and dumps core

In testMgmd, start ndbd with --core-file=0 to avoid that invalid
configuration error takes the abnormal exit path.

Use --loose prefix as the --core-file argument only exists in debug
compiled binaries.

Change-Id: I8e217846fb62eaa1e86c10c480c0283082a74a91

Author: blaudden

storage/ndb/test/ndbapi/testMgmd.cpp

@@ -321,6 +321,7 @@ class Ndbd : public Mgmd {
     args.add(connect_string.c_str());
     args.add("--ndb-nodeid=", m_nodeid);
     args.add("--foreground");
+    args.add("--loose-core-file=0");
     return Mgmd::start(working_dir, args);
   }