rx: Enter loss recovery when we retransmit

rx: Enter loss recovery when we retransmit

Since I mistakenly wrote commit 36e2d13b, RX hasn't entered congestion
avoidance when a loss event occurs. This is bad, because on todays
networks the majority of packet losses are due to some form of
congestion.

Now that the timeout code has been restructured, the chances of entering
the retransmit routine in error are much much smaller, so this code
needs to be restored.

This change reverts 36e2d13b55085c996d38b30d003296c602ef8ee3. However,
the original RX code has the problem that it assumes that all forms of
fast recovery are the same - in particular, that the call settings that
result from entering fast recovery due to a fast retransmit are
identical to those resulting from a timeout. This is not the case, and
this will be fixed in a later change.

Reviewed-on: http://gerrit.openafs.org/4866
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit e8c4fc4f37912a5d30694caef45d27374e9201e7)

Change-Id: I5ee6aa255a0b923f445dde2f1e9f0abf98dbe623
Reviewed-on: http://gerrit.openafs.org/4938
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>