Summary:
Fix warnings exposed by gcc-4.9.x's -Wshadow-compatible-local
I plan to enable this for all of fbcode, soon.
See t13698406 for justification.
Rename inner "new_insta_comm" to "comm".
This avoids the following errors:
caffe2/caffe2/mpi/mpi_common.cc:167:16: error: declaration of 'new_intra_comm' shadows a previous local [-Werror=shadow-compatible-local]
caffe2/caffe2/mpi/mpi_common.cc:162:14: error: shadowed declaration is here [-Werror=shadow-compatible-local]
Reviewed By: pietern
Differential Revision: D4544805
fbshipit-source-id: c703c3f35c71f08b4daae8491ea2518572fc8013