Make check for /dev/loop device names stricter to avoid /dev/loop-control
Make check for /dev/loop device names stricter to avoid /dev/loop-control

Recentish (2011) kernels introduced a new device called /dev/loop-control,
which causes libvirt's detection of loop devices to get confused
since it only checks for a prefix of 'loop'. Also check that the
next character is a digit

Signed-off-by: Daniel P. Berrange <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

eskultety/libvirt,nertpinx/libvirt,nertpinx/libvirt,andreabolognani/libvirt,jfehlig/libvirt,taget/libvirt,cbosdo/libvirt,datto/libvirt,fabianfreyer/libvirt,zippy2/libvirt,datto/libvirt,elmarco/libvirt,shugaoye/libvirt,zippy2/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,rlaager/libvirt,olafhering/libvirt,zhlcindy/libvirt-1.1.4-maintain,fabianfreyer/libvirt,jardasgit/libvirt,olafhering/libvirt,jfehlig/libvirt,zhlcindy/libvirt-1.1.4-maintain,eskultety/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,jfehlig/libvirt,eskultety/libvirt,crobinso/libvirt,shugaoye/libvirt,fabianfreyer/libvirt,cbosdo/libvirt,datto/libvirt,zippy2/libvirt,crobinso/libvirt,agx/libvirt,zhlcindy/libvirt-1.1.4-maintain,eskultety/libvirt,rlaager/libvirt,taget/libvirt,rlaager/libvirt,rlaager/libvirt,elmarco/libvirt,libvirt/libvirt,elmarco/libvirt,VenkatDatta/libvirt,datto/libvirt,andreabolognani/libvirt,shugaoye/libvirt,agx/libvirt,zhlcindy/libvirt-1.1.4-maintain,agx/libvirt,crobinso/libvirt,andreabolognani/libvirt,nertpinx/libvirt,andreabolognani/libvirt,taget/libvirt,datto/libvirt,jardasgit/libvirt,shugaoye/libvirt,cbosdo/libvirt,VenkatDatta/libvirt,libvirt/libvirt,libvirt/libvirt,elmarco/libvirt,zippy2/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,shugaoye/libvirt,eskultety/libvirt,taget/libvirt,zhlcindy/libvirt-1.1.4-maintain,jardasgit/libvirt,olafhering/libvirt,cbosdo/libvirt,rlaager/libvirt,jfehlig/libvirt,VenkatDatta/libvirt,crobinso/libvirt,elmarco/libvirt,olafhering/libvirt,agx/libvirt,andreabolognani/libvirt,agx/libvirt,taget/libvirt,jardasgit/libvirt,cbosdo/libvirt,nertpinx/libvirt,libvirt/libvirt