AMS: added caching DataInputStream object

DataInputStream is cached for the lmkd socket communication
Since the LmkdConnection ByteBuffer is allocated once,
no need to dynamically allocate DataInputStream,
just do a reset() before using

Bug: 184698933
Test: lmkd_unit_test - test check_for_oom tests lmkd message send to AMS
Test: statsd_testdrive 51 54 to inspect statsd logged atoms data
Change-Id: I9b65d82618654d59236c79be8cd8da66bc90c91c