qemu_vm: Fix is_paused() method

The verify_status() method raises an exception if the
vm state does not match the one passed to the function.
So this leads to massive failures in the qemu related
tests. Let's fix it by handling the exceptions raised
by verify_status() properly.

CC: Chris Evich <cevich@redhat.com>
CC: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>