Fixing tests.

src/php/ext/grpc/channel.c

test/core/end2end/fixtures/chttp2_fake_security.c

test/core/end2end/fixtures/chttp2_simple_ssl_fullstack.c

.../end2end/fixtures/chttp2_simple_ssl_fullstack_with_poll.c

...end2end/fixtures/chttp2_simple_ssl_fullstack_with_proxy.c

...nd2end/fixtures/chttp2_simple_ssl_with_oauth2_fullstack.c

...2end/tests/request_response_with_payload_and_call_creds.c

test/core/fling/server.c

test/core/security/credentials_test.c

test/core/security/fetch_oauth2.c