t1430: improve test coverage of deletion of badly-named refs

t1430: improve test coverage of deletion of badly-named refs

Check "branch -d broken...ref"

Check various combinations of

* Deleting using "update-ref -d"
* Deleting using "update-ref --no-deref -d"
* Deleting using "branch -d"

in the following combinations of symref -> ref:

* badname -> broken...ref
* badname -> broken...ref (dangling)
* broken...symref -> master
* broken...symref -> idonotexist (dangling)

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: David Turner <dturner@twopensource.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>