The 'libvirt-tmp-activewrite' bitmap is added during the 'pivot'
operation of block copy and active layer block commit operations
regardless of whether there are any bitmaps to merge, but was not
removed unless a bitmap was merged. This meant that subsequent attempts
to merge into the same image would fail.
Fix it by checking whether the 'libvirt-tmp-activewrite' would be used
by the code and don't skip the code which would delete it.
This is a regression introduced when we switched to the new code for
block commit in <20a7abc2d2d> and for block copy in <7bfff40fdfe5>. The
actual bug originates from <4fa8654ece>.
https://bugzilla.redhat.com/show_bug.cgi?id=1857735
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
