vdsm.spec: BZ 988299: Fix GlusterFS RPM dep to support GlusterFS SD

This patch fixes the GlusterFS RPM dependency needed by VDSM to
support Gluster Storage Domain feature. Recent GlusterFS RPM
re-packaging effort to better separate the client and server side
bits and availability of qemu with libgfapi support mark the
pre-req for this patch. These pre-req are now available in
F18/F19/RHEL6/Centos6 and above in the appropriate distro specific
repos. Also removing F17 dep as its End of life now.

BZ 988299 has more details, with pointers to the community
discussions around these.

Change-Id: If648feec92ed33f24f45550f016ac132a25e6923
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=988299
Signed-off-by: Deepak C Shetty <deepakcs@linux.vnet.ibm.com>
Reviewed-on: http://gerrit.ovirt.org/17994
Reviewed-by: Bala.FA <barumuga@redhat.com>
Reviewed-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/18426
Tested-by: Federico Simoncelli <fsimonce@redhat.com>