LU-7174 build: add mmap_cat to .gitignore

LU-7174 build: add mmap_cat to .gitignore

While testing patches other non-patch the new application
mmap_cat will show up with git status. To avoid adding
this by accident place thes by product files in the
proper .gitignore files.

Change-Id: I11ae5fd73ef0c5238fedf2d7a5673944af421ead
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: http://review.whamcloud.com/17845
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>