Remove useless response checks in SolidFire driver

Remove useless response checks in SolidFire driver

The main issue_api_request method in the SolidFire driver
has had a mechanism to check validity of response data for
some time now.  It checks the response and if there isn't
a valid result in the response it raises.

The problem is that we still have some cruft from the old
code that does local checking/verfication.  These checks
won't ever actually be called because of the exception, and
they create some confusion.

This patch just removes those useless checks and cleans up
the api_request calls a bit.

Change-Id: Ifbcda0f943bb0b9dc47aff25bbb9245ce361fc48
Closes-Bug: #1491485