flags is currently used for power of 2 allocation and is probably not applicable to the other storage engines. The server should error out to warn the user instead of silently ignoring it.

Sample shell session connected to a mongod running on wiredtiger engine:

> db.runCommand({ create: 'usd', flags: 0 })
{ "ok" : 1 }
> db.runCommand({ listCollections: 1 })
{
	"collections" : [
		{
			"name" : "usd",
			"options" : {
				"flags" : 0
			}
		}
	],
	"ok" : 1
}