netd: Add clang-format style config

Copied verbatim from system/core/.clang-format-4, then added

  BreakBeforeTernaryOperators: true

Since this is the default value set by the the Google style, the two
styles are still functionally identical.

Test: Checked that vim's codefmt plugin formats netd sources correctly.
Change-Id: I420a41d263f1683f7a7ebe9ff73c7e240900ed5d