build: Re-enable validateIndentation

Upstream https://github.com/mdevils/node-jscs/issues/459 got fixed
and released in node-jscs v1.5.4. Our grunt package automatically
updates to 1.5.x so we can use this now.

Fixed pre-existing violations of indentation rules.

Change-Id: Ie5d15e2e2353cd2b16ade4f4a25f9fc02e43087e