userportal, webadmin: fixed tabindexes for login pages

Since PatternFly adoption, tabbing through fields on the login pages
was erratic. Fixed to be in the proper, predictable order.

As part of fixing this, changed  UiCommonEditorVisitor to not set
tabindex on an editor if it's already set (i.e. don't override a
manually-set tabindex).

Change-Id: I434eb12b5efe003c0d1c139ad94d4d352668f403
Bug-Url: https://bugzilla.redhat.com/1154051
Signed-off-by: Greg Sheremeta <gshereme@redhat.com>