Fixes #9044 - fixes invalid mac in tests

Also do not reset invalid mac address to nil so we can propagate proper
validation error.

Fixes #7971 - DHCP hostname commutative conflict fix

Refs #3809 - Use parentheses in method definitions

Refs #3809 - Fix a few rubocop TODOs

Refs #3809 - Remove rubocop TODOs

Removed the following TODOs so that cops for these will run from now on:

Lint/AmbiguousOperator, DefEndAlignment, DeprecatedClassMethods
EnsureReturn, RequireParentheses, Void, BlockAlignment, EndAlignment,
UselessAccessModifier,...

fixes #7430 - Adds subnet mask validation

fixes #6382 - revert name change of 48bit mac address regex to fix discovery

fixes #5915 - Add support for Infiniband 64-bit MAC addresses

Fixes #5941 - Handle nil comparison object in DHCP::Record.valid?

Fixes #5637 - Don't raise lease conflicts when reading ad-hoc DHCP leases