ui: rename cloud-init root-password to password

The password field is not relevant only for root - but other users as
well.

Change-Id: I84451cc25ae14f056c673eb715eea3ea870840d5
Bug-Url: https://bugzilla.redhat.com/1126185
Signed-off-by: Shahar Havivi <shaharh@redhat.com>