mongodb: manage manage_package_repo on RHEL

manage_package_repo should be set to true, otherwise mongodb module is
not aware about Packaging specifications on RHEL.

Bug #408
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge pull request #412 from enovance/bug/408/emilienm

mongodb: manage manage_package_repo on RHEL