[storageproxyd] Dump binary buffers to log instead of stderr

Rewrites the buffer logging to print to the Android log instead of
stderr. The storageproxyd service is started by init and stderr is not
logged anywhere. Because we want to log sense data errors under normal
operation, we need to log to logcat instead of stderr.

Test: Define RPMB_DEBUG, build for qemu-trusty, run, inspect logcat
Bug: 195544379
Change-Id: Iecc0d4680420bb92c94be628789093888a2f1941
Merged-In: Iecc0d4680420bb92c94be628789093888a2f1941