See repro. We should probably just uassert for this, to avoid filling the system log with unnecessary backtraces.

Repro steps:
1. start mongod
2. start mongo shell
3. issue shell commands:

> use $bad
switched to db $bad
> db.createCollection("a")
{
	"operationTime" : Timestamp(0, 0),
	"ok" : 0,
	"errmsg" : "cannot do createCollection on namespace with a $ in it: $bad.a",
	"code" : 17320,
	"codeName" : "Location17320"
}

4. observe backtrace in mongod system log

Expected behavior: step 4 should observe no backtrace.