Remove Puppet unit tests for version 2.7

Puppet 2.7 is no longer supported, and the major distros
are now up to 3.x.  So it makes sense to remove testing
against this version in the gate.

However, there are comments here that Puppet 2.7 support
was planned to continue until spring 2015.  So I will leave
it up to the group on whether or not we are close enough
to that threshold to remove it.

Change-Id: I3791328d743f2424d84aad1d206a7317ba5a84e3
Merge "Remove Puppet unit tests for version 2.7"