test: don't skip when common.mustCall() is pending

The test parallel/test-dgram-multicast-set-interface.js was
calling common.skip() on hosts that do not support IPv6. However,
by this point, there were several outstanding common.mustCall()
invocations. The process.exit() in common.skip() triggered
those common.mustCall()s as errors.

Fixes: nodejs/node#15419
PR-URL: nodejs/node#15421
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Daniel Bevenius <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Brian White <[email protected]>
Reviewed-By: Sakthipriyan Vairamani <[email protected]>

Author: cjihrig

test/parallel/test-dgram-multicast-set-interface.js

@@ -72,18 +72,11 @@ const dgram = require('dgram');
   }));
 }
 
-<<<<<<< HEAD
 // If IPv6 is not supported, skip the rest of the test. However, don't call
 // common.skip(), which calls process.exit() while there is outstanding
 // common.mustCall() activity.
 if (!common.hasIPv6)
   return;
-=======
-if (!common.hasIPv6) {
-  common.skip('Skipping udp6 tests, no IPv6 support.');
-  return;
-}
->>>>>>> 4ae0afb12b... dgram: added setMulticastInterface()
 
 {
   const socket = dgram.createSocket('udp6');