repl/dbcase failure due to listdatabases consistency exception

<http://buildbot.mongodb.org/builders/OS%20X%2010.5%2064-bit%20DUR%20ON/builds/218/steps/test_6/logs/stdio>

m31001| Fri Jun 3 01:41:12 [replslave] An earlier initial clone of 'dbNAme' did not complete, now resyncing.
m31001| Fri Jun 3 01:41:12 [replslave] resync: dropping database dbNAme
Fri Jun 3 01:41:12 uncaught exception: listDatabases failed:{
"assertion" : "db already exists with different case other: [dbNAme] me [dbname]",
"assertionCode" : 13297,
"errmsg" : "db assertion failure",
"ok" : 0
}

The listDatabases command attempts to switch to each available database it is aware of. But its list of databases may be out of date, causing it to attempt to switch to a database having a name conflict with an existing database and triggering an assertion.

We can either change listDatabases so it can't assert in this case or fix the test to work around this issue.