Add contains type tidy check

On general container usage, contains() is more descriptive than count()
> 0.  We have one violation of this, fix it and enable the check.

Tested: Clang-tidy passes.

Change-Id: Ib5702ef97c6da033b6587c9cfebbe30dfbfe80b4
Signed-off-by: Ed Tanous <edtanous@google.com>
diff --git a/.clang-tidy b/.clang-tidy
index 308c3f9..ffa6589 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -280,6 +280,7 @@
 readability-avoid-const-params-in-decls,
 readability-braces-around-statements,
 readability-const-return-type,
+readability-container-contains,
 readability-container-data-pointer,
 readability-container-size-empty,
 readability-convert-member-functions-to-static,