Set cinder's multiple_backends param also in HA controller

For non-HA controller it already works as it should - when more than
one backend is checked in the wizard, multiple_backends parameter is
set to true. For HA controller this parameter override was missing and
this commit adds it.
Merge pull request #364 from jistr/ha_multiple_backends

Set cinder's multiple_backends param also in HA controller
BZ #1155768: Hash params need textarea for proper load/store

https://bugzilla.redhat.com/show_bug.cgi?id=1155768

When a hash parameter is encountered, it must use a textarea instead of
a textfield, otherwise the yaml will be malformed. This also pulls these
fields out into a partial.
Merge pull request #365 from bcrochet/bz/1155768

BZ #1155768: Hash params need textarea for proper load/store