db.dropDatabase() through mongos while a migration is happening can lead to wrong "show dbs" output

Steps to reproduce:

1. Bring up a sharded cluster with at least 2 shards
2. Insert a lot of data, such that the collection will be split and chunks migrated.
3. Run "show dbs" (I am using the "blah2" database):

mongos> show dbs

admin	(empty)

blah2	4.9052734375GB

config	0.1875GB

test	0.203125GB

4. Interrupt the data load script, or wait until it completes.
5. While a migration is happening, attempt "db.dropDatabase()" through a mongos
5.a. The first time I tried this, I got:

mongos> db.dropDatabase()

{

	"assertion" : "collection's metadata is undergoing changes. Please try again.",

	"assertionCode" : 13331,

	"errmsg" : "db assertion failure",

	"ok" : 0

}

5.b. I immediately retried and got:

mongos> db.dropDatabase()

{

	"assertion" : "shard state missing for blah2.foo",

	"assertionCode" : 10176,

	"errmsg" : "db assertion failure",

	"ok" : 0

}

5.c. The third try worked:

mongos> db.dropDatabase()

{ "dropped" : "blah2", "ok" : 1 }

6. Run "show dbs" again:

mongos> show dbs

admin	(empty)

blah2	5.951171875GB

config	0.1875GB

test	0.203125GB

7. Verify that data files are missing for all shards (in my case they were)
8. Insert new data with "db.bar.insert(

)"
9. Run "show dbs" again

mongos> show dbs

admin	(empty)

blah2	6.154296875GB

config	0.1875GB

test	0.203125GB

Expected output:

• In step 6, "blah2" database should not show up
• In step 9, "blah2" database should not be so large (one would expect it to be 2GB on disk)