[mongo] repairing of mongodb.can_connect check

[cryptspirit]

Connection to database going in db.command function, but the call of this function happens outside of exception block. The check can't catch unreachable instances and integration check mongodb.can_connect doesn't work properly

[degemer]

Thanks for the PR @cryptspirit !
I think there may be an issue if the connection requires authentification though: status = db.command('serverStatus', tcmalloc=collect_tcmalloc_metrics) happens before db.authenticate(username, password).

What do you think of something like this instead ?

try:
     status = db.command('serverStatus', tcmalloc=collect_tcmalloc_metrics)
except Exception:
    self.service_check(
        self.SERVICE_CHECK_NAME,
        AgentCheck.CRITICAL,
        tags=service_check_tags)
    raise
else:
    self.service_check(
        self.SERVICE_CHECK_NAME,
        AgentCheck.OK,
        tags=service_check_tags)

[cryptspirit]

@degemer right. there is need to add separate exception block for serverStatus execution

[degemer]

@cryptspirit would you like to update your PR with this change then ? (if you don't have the time, we can open another one)

[cryptspirit]

I will

[degemer]

Thank you @cryptspirit ! (and sorry for the delay)
Merging.