Fix a default value change causing datagrid unit tests to fail.
Fix a default value change causing datagrid unit tests to fail.

The recent introduction of an "All" page on AlphanumericDataGrid, which
is now the default, broke the unit tests for the /users/ page. The test
assumed the original default of showing usernames starting with "A" was
still in effect. We're now using the appropriate defualt for listing all
users.

bkochendorfer/reviewboard,reviewboard/reviewboard,KnowNo/reviewboard,davidt/reviewboard,davidt/reviewboard,beol/reviewboard,sgallagher/reviewboard,chipx86/reviewboard,KnowNo/reviewboard,reviewboard/reviewboard,beol/reviewboard,custode/reviewboard,chipx86/reviewboard,KnowNo/reviewboard,beol/reviewboard,beol/reviewboard,custode/reviewboard,custode/reviewboard,bkochendorfer/reviewboard,sgallagher/reviewboard,reviewboard/reviewboard,sgallagher/reviewboard,brennie/reviewboard,brennie/reviewboard,brennie/reviewboard,bkochendorfer/reviewboard,chipx86/reviewboard,brennie/reviewboard,KnowNo/reviewboard,chipx86/reviewboard,bkochendorfer/reviewboard,reviewboard/reviewboard,davidt/reviewboard,custode/reviewboard,davidt/reviewboard,sgallagher/reviewboard