libafs: Do not specify an Rx busy channel error

libafs: Do not specify an Rx busy channel error

Do not specify an error for Rx busy channels in libafs, so we do not
get notified of busy channel notifications. The current code just
specifies RX_CALL_TIMEOUT for the busy channel error, which has
problems (in particular, for RXAFS calls that are not wrapped in an
afs_Analyze loop). So, disable this behavior.

This is a 1.6-specific change. The master branch will instead get
fixes for this functionality, and it will get turned on in 1.6 again
as appropriate.

Change-Id: I0ed292a61ba4c8d0e59017b3dfaadc88d17591e6
Reviewed-on: http://gerrit.openafs.org/4460
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>