Revert "liblog: disable header_abi_checker"

All planned changes to liblog have been made, so it's time to
re-enable this.

This reverts commit 896fb9e5.

Bug: 150608248
Test: build
(cherry picked from commit cfcf684c)
Merged-In: I93553da6207976c83091f21936b0ecdd31e82848
Change-Id: I93553da6207976c83091f21936b0ecdd31e82848