virsh.dompmsuspend: Code adjust and log level fix

1. Move variable 'need_mkswap' out of if block to reduce the judge levels.
2. Fix the debug log level.

Signed-off-by: Yanbing Du <ydu@redhat.com>
Merge pull request #279 from will-Do/dompmsuspend

virsh.dompmsuspend: Code adjust and log level fix