export api for resetting policy to init state

Policies are changed through time, but can't be resetted to init state
unless restarting mom.
expose this api to address this problem.

Change-Id: I298a53e5b90bc30e2b9c351f5907203707c21324
Signed-off-by: Royce Lv<lvroyce@linux.vnet.ibm.com>
Signed-off-by: MeiLiu <liumbj@linux.vnet.ibm.com>
Reviewed-on: http://gerrit.ovirt.org/12518
Reviewed-by: Adam Litke <agl@us.ibm.com>