Fixes many of the Service API Tests

Handles logic issues in the cassandra storage when formatting
retrieved services - to handle None conditions.

Error block updated to return a 500 on unhandled status errors.

Pecan responses updated to not return null

Closes-Bug: 1389790
Closes-Bug: 1389795
Closes-Bug: 1394775
Change-Id: Ib299b882ff4181ac281f33d496fd74b7d66cd1d6