Fix/suppress statsd google-explicit-constructor warnings

* Add explicit to conversion constructors/operators
* Remove redundant explicit of copy constructors

Bug: 28341362
Test: make with WITH_TIDY=1 DEFAULT_GLOBAL_TIDY_CHECKS=-*,google-explicit-constructor
Change-Id: Ifd0ca9a1afe4a2cb0456a36c69bee1633af5a93a
8 files changed