Remove debug log from NetworkStatsService

This change reverts aosp/1777887. The exception was used to get
the stack while the mMobileIfaces contains null interface, and
currently mMobileIfaces is protected by making it volatile so
it is fine to be removed.

Also, fix style error in NetworkStatsServiceTest

Test: build, FrameworksNetTests
Change-Id: I8435354f8cfd05589c0231f3bb8cbaa66c0525cf
2 files changed