Performance problems with "Assign Role" or "Remove Assigned Role"

[posixeleni]

When we try to remove an Assigned Role it spins and when we refresh the page it does nothing. Discovered while meeting with @mcrosas when looking into AJPS.

[pdurbin]

On my laptop on commit ab0b268 (pre-4.1 release) I loaded up production data and played around with granting and revoking a role on a dataverse ("togo") with 32 datasets and 194 files. To me it's unacceptably slow even with Solr is down, taking nearly 10 seconds:

	Solr Up	Solr Down
grant	0m25.653s	0m9.699s
revoke	0m23.539s	0m9.968s

Obviously, at ~25 seconds it's crazy slow when Solr is up, which is related to #50.

I'm not sure what our target is for response time for the operation to complete but I guess we'll try to make it as fast as we can. ab0b268 contains the script I'm testing with.