This chunk of code below repeated in several functions, factor it into
a helper method virDomainLiveConfigHelperMethod to eliminate duplicated code
based on Eric and Adam's suggestion. I have tested it for all the
relevant APIs changed.
Signed-off-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NLei Li <lilei@linux.vnet.ibm.com>