virsh: common code for parsing --seconds

virsh: common code for parsing --seconds

Several virsh commands ask for a --timeout parameter in
seconds, then use it to control interfaces that operate on
millisecond limits; I also plan on adding a 'virsh event'
command that also does this.  Factor this into a common
function.

* tools/virsh.h (vshCommandOptTimeoutToMs): New prototype.
* tools/virsh.c (vshCommandOptTimeoutToMs): New function.
* tools/virsh-domain.c (cmdBlockCommit, cmdBlockCopy)
(cmdBlockPull, cmdMigrate): Use it.
(vshWatchJob): Adjust timeout scale.

Signed-off-by: Eric Blake <eblake@redhat.com>