[FaceRest][Dashboard] Add "numberOfBadHosts" to each elements of serverStatus in overview

In the previous implementation "numberOfBadHosts" exists only in
each host groups, then the "numberOfBadHosts" for a server is
calculated by JavaScript side. But a host may be joined to multiple
host groups. In this case such host will be duplicated in the value.
[Dashboard View] Remove needless code

"numberOfBadHosts" for a server is counted by the server side.
[FaceRest][DBClientHatohol][DashboardView] Add "numberOfBadTriggers" to each elements of serverStatus in overview.json

The reason is same with e39338c445b28548911f0e58c802d89a5abc9fa0.
[DashbordView] Remove needless code

The number of bad triggers for a server is counted by the server side.
[DBClientHatohol] Use brace for a long if - else block
[testDBClientHatohol] Split a test of getNumberOfBadTriggers() for TRIGGER_SEVERITY_ALL from test_getNumberOfTriggersBySeverity()
Merge pull request #236 from project-hatohol/fix-wrong-number-of-bad-hosts

Fix wrong number of bad hosts & triggers of a server