Refactors initial directory scan to be dryer

This change collapses a bunch of manual calls to scanDir with a map and
a loop. This makes things a little more readable and easier to update
going forward.

Bug: NA
Test: boots without issue.
Merged-In: I81fb7a9474894d0bceecb6b0ef7a64d047a40c14
Change-Id: I81fb7a9474894d0bceecb6b0ef7a64d047a40c14