6465: Noticed a slight dip in code coverage in two areas and added tests to cover...

6465: Noticed a slight dip in code coverage in two areas and added tests to cover those situations. Details:
1. Removal of integration "Test dashboard button all {jobs}" resulted in no test at all to visit /jobs page.
Added a controller test for this.
2. Not visiting the hash match page when only one collection matches (the controller test just verified the redirection),
resulted in the unforeseen side effect of not testing preview allowed status for a file name extention that is not listed
in application_mimetypes_with_view_icon (tar file in this case). Added this to test.