Disable log for per uid blocked status changed event

This consumes ~3.5% system logs, however it is not very useful
when debugging since similar information could be obtained from
dumpsys {connectivity|netpolicy}. Thus, remove the log.

Test: manual
Bug: 135504481
Change-Id: I04d2b7402f892546722fe6868c521afd9534f183
Merged-In: I04d2b7402f892546722fe6868c521afd9534f183
(cherry picked from commit 21a352f7)