Don't use ceph-devel on Fedora

A previous commit changed the spec to use librbd1-devel on
RHEL-7, since this replaces ceph-devel from RHEL-6:

  commit 6cfc8834
  Author: Peter Krempa <pkrempa@redhat.com>
  Date:   Thu Mar 5 11:40:54 2015 +0100

    spec: Enable RBD storage driver in RHEL-7

    Use correct package names too as they differ.

RHEL-7 inherited this rename from Fedora though, so it should
have also made Fedora use the new names.

This was missed, because Fedora still provides a (deprecated)
back-compat RPM for ceph-devel that just pulls in librbd1-devel
(and others).

Fixing this stops libvirt pulling Java into the build root in
Fedora.
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
(cherry picked from commit 47275940)

libvirt.spec.in

@@ -359,7 +359,7 @@ BuildRequires: parted-devel
 # For Multipath support
 BuildRequires: device-mapper-devel
 %if %{with_storage_rbd}
-    %if 0%{?rhel} >= 7
+    %if 0%{?fedora} || 0%{?rhel} >= 7
 BuildRequires: librados2-devel
 BuildRequires: librbd1-devel
     %else