(PUP-2950) enabling rubocop Style/AndOr cop in pops directory

This commits enables AndOr cop only in lib/puppet/pops directory. This cop
bans the use of and and or keywords in favor of && and ||. We have
chosen this directory as a test case to evaluate the utility of enabling
AndOr on the complete codebase. We inherit from the base rubocop file, so all
the other cops remain enabled. At a future date, when AndOr is enabled
systemwide, this file may be removed (if no other specialization exists on pops
directory).

It changes all code that uses and and or keywords to use && and
|| instead. Note that this commit only fixes the lib/puppet/pops directory.