Update libstatssocket/pull API council feedback

ALso, removes KeyValuePairs support from libstatssocket

Test: make
Test: atest libstatssocket_test
Test: atest statsd_test
Test: atest LibStatsPullTests
Test: statsd_testdrive 10068
Change-Id: I3a5d0e66f00cea5897e0db33cb769bf6ea67f320
14 files changed