Description of problem:
Migration hang when the guest is with glusterfs volume and the destination host can't access to this glusterfs volume.

Version-Release number of selected component (if applicable):
libvirt-1.1.1-10.el7.x86_64
qemu-kvm-1.5.3-10.el7.x86_64
glusterfs-3.4.0.36rhs-1.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Create a guest with xml below on glusterfs client A:
# virsh dumpxml r7|grep disk -A 6
    <disk type='network' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source protocol='gluster' name='gluster-vol1/rh7-qcow2.img'>
        <host name='10.66.82.251' port='24007'/>
      </source>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    </disk>

2. Do live migration to another glusterfs client B successfully.
# virsh migrate --live --verbose r7 qemu+ssh://10.66.5.93/system --unsafe
root.5.93's password: 
Migration: [100 %]

3. Do live migration back to this machine A successfully.
# virsh migrate --live --verbose r7 qemu+ssh://10.66.4.217/system --unsafe
root.4.217's password: 
Migration: [100 %]

4. On the glusterfs client B, uninstall the glusterfs package.
# rpm -qa|grep gluster
glusterfs-libs-3.4.0.36rhs-1.el7.x86_64
glusterfs-api-3.4.0.36rhs-1.el7.x86_64

5. Redo the live migration to glusterfs client B, the migration hang.
# virsh migrate --live --verbose r7 qemu+ssh://10.66.5.93/system --unsafe
root.5.93's password:

Actual results:
In step5, the migration hang.

Expected results:
In step5, the virsh migrate command line should return back with suitable error message.