Currently "bitbake universe -c fetch" will error if every task in the system
doesn't have a fetch task. This seems unreasonable so filter the list based
upon whether the task exists. This implementation does assume if a task exits
for a given provider name, it can run, even if the preferred provider that
ends up getting built might be the namespace without the task. This is unlikely
to be a real world issue at this point.
(Bitbake rev: 438986f4e39974930ee3205ca4c4d620090e57bb)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>