Set Tempest storage protocol and vendor w/o setting driver

Set TEMPEST_STORAGE_PROTOCOL and TEMPEST_VOLUME_VENDOR if
they are changed from their defaults, or if
TEMPEST_VOLUME_DRIVER is changed.

This maintains the current behavior of setting these options if
TEMPEST_VOLUME_DRIVER is set to something other than "default".

Change-Id: I1fb7f5db0446f97de48b97a6f451882cc51c51a4
Merge "Set Tempest storage protocol and vendor w/o setting driver"