B #5139: Do not overwrite existing vnc password (#369)
B #5139: Do not overwrite existing vnc password (#369)

(cherry picked from commit 08d4f89d99fc70c5ba54dfc9f1ca68827320c25b)

OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one,OpenNebula/one