Refactoring HDP plugins to allow multiple Zookeeper servers

These changes are reflected in both the 1.3.2 and 2.0.6 versions of the
HDP plugin.

Changes
* fixing tests
* changing default cluster templates to allow multiple zookeeper servers
* changing zookeeper validations to allow multiple servers

Closes-Bug: #1260835
Change-Id: I5645db95ad3cb44e1d9e5db32c996280ba2d820a
Merge "Refactoring HDP plugins to allow multiple Zookeeper servers"