packaging: RGW depends on /etc/mime.types

packaging: RGW depends on /etc/mime.types

If the mimecap RPM or mime-support DEB is not installed, then the
/etc/mime.types file is not present on the system. RGW attempts to read
this file during startup, and if the file is not present, RGW logs an
error:

  ext_mime_map_init(): failed to open file=/etc/mime.types ret=-2

Make the radosgw package depend on the mailcap/mime-support packages so
that /etc/mime.types is always available on RGW systems.

http://tracker.ceph.com/issues/11864 Fixes: #11864

Signed-off-by: Ken Dreyer <kdreyer@redhat.com>