Host Set API and misc test fixes

Client update:

- Add Host Set API

Fixes in Tests:
- Allow setting domain and cpg_ldlayout_ha for tests
- Reduce volume size for tests
- Remove test_ prefix from files without tests
- Add VLUN and host set check in flask deleteHost
- Make some error codes and messages consistent with the array.

Change-Id: Id203e7816ad06ce5ebd8df877b3ce626883d4718