bitbake: fetch2: Improve mirror looping to consider more cases

bitbake: fetch2: Improve mirror looping to consider more cases

Currently we only consider one pass through the mirror list. This doesn't
catch cases where for example you might want to setup a mirror of a mirror
and allow multiple redirection. There is no reason we can't support this
and the patch loops through the list recursively now.

As a safeguard, it will stop if any duplicate urls are found, hence
avoiding circular dependency looping.

(From Poky rev: 0ec0a4412865e54495c07beea1ced8355da58073)

(Bitbake rev: e585730e931e6abdb15ba8a3849c5fd22845b891)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>