virDomainHasDiskMirror() currently detects only jobs that add the mirror
elements. Since some operations like migration are interlocked by
existing block jobs on the given domain the check needs to be
instrumented to check regular jobs too.

This patch renames virDomainHasDiskMirror to virDomainHasDiskBlockjob
and adds an argument that allows to select that it returns true only for
block copy jobs as those interlock making the domain persistent.

Other two uses trigger on any block job type.
Signed-off-by: NShanzhi Yu <shyu@redhat.com>
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>