Horizon: service: Default to v2 API

Horizon: service: Default to v2 API

Horizon service definition hardcodes the API version to v3, and
also overrides the value in our reclass model during interpolation.
Adjust the default to '2'.

While at it, move 'reclass' patching later in `salt.sh`, after
the salt formula packages are installed.

JIRA: FUEL-284

Change-Id: I6f63b4d00ae85c82b076b3efef857e7cc4f3fd35
Signed-off-by: Ting Wu <ting.wu@enea.com>
Signed-off-by: Junaid Ali <junaidali.yahya@gmail.com>
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>