Fixed issues on Admin->Users index page

The default view of the users' index file was previously causing some confusing issues where pagination controls appeared, but did nothing. To resolve that, I changed the query used to do the count for that view type, as the LIMIT parameter doesn't work to affect the count of records returned. Additionally, I fixed a minor display issue in which the "Login as" cell in the table wouldn't show up (with nothing in it) for users that don't have permissions in the table, causing the grey background to not reach the end of those lines of the table.