Added tmpfiles.d for rgw: templated user and group.

Added tmpfiles.d for rgw: templated user and group.

tmpfiles.d are part of system.d and define how temporary directories are setup.
rgw needs a socket directory. To do this we template tmpfiles.d user and group
for rgw and fill in the values using autotools.

Note1: Added to spec file.
Note2: Name changed to rgw from radosgw as is preferred name by Sage.
Note3: Adds configure options
    --with-rgw-user=UserName
    --with-rgw-group=GroupName
Note4: Defaults set for debian
Note5: spec file overrides defaults for redhat and suse

Signed-off-by: Owen Synge <osynge@suse.com>