Revert previous two commits.

Revert "Fix DoS_tests to work with new SendMessageCSMain()"
Revert "Split SendMessages into two functions.  Require cs_main for one of them."

Conflicts:
	src/net.cpp
Split SendMessages handler in two - one for handling cs_main-dependent tasks.

Also made the main.cpp SendMessages wait on the lock instead of TRY_LOCK().