These are test images to build all recipes in layer. Renaming them makes
them refect what they are. Moreover we can rename the ptest images to
match OE-Core naming conventions for meta-oe/meta-perl/meta-python

Signed-off-by: Khem Raj <raj.khem@gmail.com>
(cherry picked from commit 0cb01805

)
Signed-off-by: Armin Kuster <akuster808@gmail.com>