On the Gluster site there is a QEMU repo I'll send you the link latter today. But essentially CentOS doesn't include the Gluster client or libraries so they can't compile against it.
I'm not sure why CentOS and Scientific Linux don't include it but I think it might just be an over site since Gluster 3.4 is new set of packages which were added in the latest release of RHEL 6.
In truth you can simply unpack the source RPM and rebuild it with Gluster support its not difficult but I don't remember the flags you need to pass the rpmbuild command off the top of my head. That said I'd probably use the ones off the Gluster site any way. 
If you are using Gluster 3.5 the ones included in RHEL are incompatible because Gluster still has large API changes between minor releases and they were compiled against 3.4. 

Also Gluster 3.5 is a brand new release so I wouldn't rule out the possibility of a bug. So if the Gluster enabled QEMU rpms don't help you may need to inquire on the Gluster mailing list.