Merge pull request #3815 from murgatroid99/node_increase_coverage

binding.gyp

src/node/ext/call.cc

src/node/ext/call.h

src/node/ext/call_credentials.cc

src/node/ext/channel.cc

src/node/ext/channel.h

src/node/ext/channel_credentials.cc

src/node/ext/server.cc

src/node/ext/server_credentials.cc

src/node/interop/interop_client.js

src/node/src/client.js

src/node/src/common.js

src/node/src/credentials.js

src/node/test/call_test.js

src/node/test/channel_test.js

src/node/test/credentials_test.js

src/node/test/health_test.js

src/node/test/interop_sanity_test.js

src/node/test/surface_test.js

templates/binding.gyp.template