[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
AOSP-Change: 1242601
Change-Id: I01c0191d5b89942fa69b167b8a6b40ed2821300b
Merged-In: I92d214f4648fec6be13e04147290ecdd156fab4e
(cherry picked from commit b9565c7d)