bb-edit: only edit existing files
bb-edit: only edit existing files

It seems that BBINCLUDED can list every possible path in BBPATH, so not all
are going to exist. Only edit the ones that do.

Signed-off-by: Christopher Larson <4c8c411260e601995081b113a5ef94a26eff2b25@mentor.com>

kergoth/bb,rossburton/bb,kergoth/bb,rossburton/bb