blockpull: Restart libvirtd after cleanup glusterfs

After several test runs, gluster cases could got fail for start vm
with error:

  error : virStorageFileBackendGlusterInit:611 : out of memory

this will block the following gluster testing cases, the problem could
be on libgfapi, restart libvirtd in test case to help avoid this.

Signed-off-by: Wayne Sun <gsun@redhat.com>