webadmin: ovirt-node reinstall/approve should use root user

While admin is local node user that should not be
used remotely when upgrading or reinstalling oVirt
Node.

Change-Id: Ia85bf1cfb96513f22629d9cb8fb3028c4446b5d2
Bug-Url: https://bugzilla.redhat.com/1080976
Signed-off-by: Ravi Nori <rnori@redhat.com>