setmem: add the new options to "virsh setmem" command

setmem: add the new options to "virsh setmem" command

This patch adds the new options (--live and --config)  to "virsh setmem" command.
The behavior of above options is the same as that of "virsh setvcpus" and so on.
That is, when the --config option is specified, a modification is effective for
the persistent domain. Moreover we can modify the memory size of inactive domains
as well as that of active domains.

Signed-off-by: Taku Izumi <izumi.taku@jp.fujitsu.com>