Fix dependency cycle between osquery_events and osquery_tables_events_eventstable

[Smjert]

osquery_events, specifically the audit files (auditnetlink and so on), access gflags that are defined in process_events.cpp compiled under osquery_tables_events_eventstable, and so it depends on osquery_events. At the same time osquery_tables_events_eventstable depends on osquery_events, because it's where the publishers of events reside.

This causes a linker error when one depends on osquery_events and doesn't want to depend on osquery_tables_events_eventstable.