adb: parse tcp socket specs with base::ParseNetAddress.

libbase already has IPv6-aware address parsing, so use it instead of
adb's handrolled IPv4-only parsing.

Bug: http://b/31537253
Change-Id: I4e9ce56b55d7d02787c0fa67b724490bf49ce479
Test: mma && adb start-server && \
      adb -L 'tcp:[::ffff:127.0.0.1]:5037' devices && \
      adb -L 'tcp:localhost:5037' devices && \
      adb -L 'tcp:127.0.0.1:5037' devices && \
      adb -L 'tcp:5037' devices && \
      $ANDROID_HOST_OUT/nativetest64/adb_test/adb_test