When there is no error body return the HTTP reason

Return the response reason when there is no message body to return.

DocImpact
Change-Id: Ia60da4f04b059a13fcbe0059bb42fd77f272d8aa
Closes-Bug: 1248773
Fix usage of v1 and v2 availability zones

Change usage of availability zones in client. V2 client should
use appropriate version of manager of availability zones.

Also change tests of v2 availability zones to test version 2
instead of one more time test v1 availability zones.

Change-Id: Iec3863a105a20f876a303f789cc1edfafa58f4df
Closes-Bug: #1290956
Merge "Fix usage of v1 and v2 availability zones"
Merge "When there is no error body return the HTTP reason"