Bump src/gnatsd

Bump apcera/gnatsd:
  Derek Collison:
     Need to flush the clients ( Travis Success: https://travis-ci.org/apcera/gnatsd/builds/15371636 )
     go fmt fix ( Travis Failed: https://travis-ci.org/apcera/gnatsd/builds/15370771 )
     1.2 only ( Travis Failed: https://travis-ci.org/apcera/gnatsd/builds/15370594 )
     go vet fixes for 1.2 ( Travis Unknown )
     fixup for change to go vet ( Travis finished: https://travis-ci.org/apcera/gnatsd/builds/15369607 )
     Clean up after ourselves ( Travis Failed: https://travis-ci.org/apcera/gnatsd/builds/15369077 )
     fix for race in test ( Travis Failed: https://travis-ci.org/apcera/gnatsd/builds/15368501 )
     Move to https for git clone ( Travis Failed: https://travis-ci.org/apcera/gnatsd/builds/15367409 )
     travis fixups ( Travis finished: https://travis-ci.org/apcera/gnatsd/builds/15367264 )
     Added in go get directive ( Travis Failed: https://travis-ci.org/apcera/gnatsd/builds/15366572 )
     Fixed slice panic on MSG_ARG split buffer ( Travis Failed: https://travis-ci.org/apcera/gnatsd/builds/15365922 )
     Bumped version ( Travis Success: https://travis-ci.org/apcera/gnatsd/builds/15248823 )
     Removed setting the Read or Write Buffers. ( Travis Unknown )
     Use shortcut ( Travis Success: https://travis-ci.org/apcera/gnatsd/builds/14171365 )