Revert "logd: validate and fill in socket credentials"

We don't want to fake socket credentials if they were not provided by
the kernel.  If there is a bug preventing us from reading the
credentials then it must be solved directly.

Test: logd, liblog unit tests
Test: boot and ensure overflow uid doesn't show up

This reverts commit c4e4823b.

Change-Id: I683129a8a214637635f163ae25c39bb8a47cd50f