PM / Hibernate: Thaw kernel threads in SNAPSHOT_CREATE_IMAGE ioctl path

commit fe9161db2e6053da21e4649d77bbefaf3030b11d upstream.

In the SNAPSHOT_CREATE_IMAGE ioctl, if the call to hibernation_snapshot()
fails, the frozen tasks are not thawed.

And in the case of success, if we happen to exit due to a successful freezer
test, all tasks (including those of userspace) are thawed, whereas actually
we should have thawed only the kernel threads at that point. Fix both these
issues.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>