bozo: cap retry delay

Cap the retry delay to a reasonable amount of time instead
of just doubling the delay until it reaches 16 hours.

Reviewed-on: http://gerrit.openafs.org/10148
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 21c8f4809ee7af9d2ec76cb37747183cee0c0d33)

Change-Id: If10880ba5411af0ea66bcb50c8cce13f4155f2ad
Reviewed-on: http://gerrit.openafs.org/10199
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>