ceph.spec.in: create /var/log/ceph/stat dir

the logrotate config expects a var/log/ceph/stat dir - create it.

index a74702d..908a65b 100644
@@ -73,6 +73,7 @@ chmod 0644 $RPM_BUILD_ROOT%{_sysconfdir}/ceph/

sample.ceph.conf
install -m 0644 -D debian/ceph.logrotate $RPM_BUILD_ROOT%{_sysconfdir}/
logrotate.d/ceph
mkdir -p $RPM_BUILD_ROOT%{_localstatedir}/lib/ceph/tmp/ mkdir -p $RPM_BUILD_ROOT%{_localstatedir}/log/ceph/
+mkdir -p $RPM_BUILD_ROOT%{_localstatedir}/log/ceph/stat

%clean
rm -rf $RPM_BUILD_ROOT