org.conf: set opkg feed URI to external

Comment out the internal feed URI set operation to allow the external
URI applied in meta-nilrt:conf/distro/nilrt.inc to stick.

Signed-off-by: Alex Stewart <[email protected]>

Revert "build-services.bbclass: don't invalidate do_fetch sstate"

This reverts commit 9bf010f.

Turns out we actually need this to avoid stale BS export data.

Signed-off-by: Ioan-Adrian Ratiu <[email protected]>