actions: bug fix in lambdas in checkBan, because getBansMerged could return None (purge resp. asynchronous addBan), make the logic all around more stable;
test cases: extended with test to check action together with database functionality (ex.: to verify lambdas in checkBan);
database: getBansMerged should work within lock, using reentrant lock (cause call of getBans inside of getBansMerged);
Test cases fixed:
	testFail2BanExceptHook - use local sys.__excepthook__ to check was really executed and prevent write error in stderr.
code review
few confusing merge info helper
Merge pull request #839 from sebres/fix-none-getattempt-lambda

Fix none getattempt lambda (close #838,  close #848)