Change KernelUidCpuTimeReader Slog.wtf to Slog.e

There is a known issue in the kernel uidcputime module that triggers
the WTF, which has a cost to the system. Convert to a regular log
instead.

Bug:28950306
Change-Id: I7cbb3138f644075f0d9d65ce8b52bd835eb270fd
(cherry picked from commit 82a4d6f9)