Only show one deny button & make them look identical

Never show both "deny" and "deny & don't ask again" buttons in the same
prompt. Make both buttons look identical by using the same style and
text. Allow backing out or clicking outside of the dialog to leave the
current dialog. Add new result to distinguish between being denied and
prompt being cancelled

Test: PermissionsHostTest
Change-Id: I66d699fb406901941ffd23451bba45feaff0535a