php: add php7 to jenkins basic and interop tests

...ckerfile/interoptest/grpc_interop_php/Dockerfile.template

...kerfile/interoptest/grpc_interop_php7/Dockerfile.template

templates/tools/dockerfile/php7_deps.include

templates/tools/dockerfile/php_common_deps.include

...tools/dockerfile/test/php7_jessie_x64/Dockerfile.template

tools/dockerfile/interoptest/grpc_interop_php/Dockerfile

tools/dockerfile/interoptest/grpc_interop_php7/Dockerfile

...dockerfile/interoptest/grpc_interop_php7/build_interop.sh

tools/dockerfile/test/php7_jessie_x64/Dockerfile

tools/run_tests/run_interop_tests.py

tools/run_tests/run_tests.py