Fixed lint errors

src/node/.jshintrc

src/node/examples/math_server.js

src/node/examples/perf_test.js

src/node/examples/stock_server.js

src/node/index.js

src/node/interop/interop_client.js

src/node/interop/interop_server.js

src/node/package.json

src/node/src/client.js

src/node/src/common.js

src/node/src/server.js

src/node/test/call_test.js

src/node/test/channel_test.js

src/node/test/constant_test.js

src/node/test/end_to_end_test.js

src/node/test/interop_sanity_test.js

src/node/test/math_client_test.js

src/node/test/surface_test.js