[SP19] Reduce log when set limit and request stats update

setLimit can be ignored if the quota is unlimited and not
changed, and the log could be omitted since it will still be
logged in HAL. Request stats update will print error log in
service if it is not correctly responded in time.

Test: atest TetheringTests
Test: manual
Fix: 149735152

Change-Id: I01c0191d5b89942fa69b167b8a6b40ed2821300b