Ensure .tf_configure.bazelrc is written to root of TF repo.

Had issues when running configure.py script from outside of TF repo. Ensuring
that the .bazelrc file from configure is written to base repo directory.

PiperOrigin-RevId: 170748513

configure.py

@@ -30,7 +30,8 @@ try:
 except ImportError:
   from distutils.spawn import find_executable as which
 
-_TF_BAZELRC = '.tf_configure.bazelrc'
+_TF_BAZELRC = os.path.join(os.path.dirname(os.path.abspath(__file__)),
+                           '.tf_configure.bazelrc')
 _DEFAULT_CUDA_VERSION = '8.0'
 _DEFAULT_CUDNN_VERSION = '6'
 _DEFAULT_CUDA_COMPUTE_CAPABILITIES = '3.5,5.2'