cleanup potpourri.h references

Clean up references to a header file which was removed some time ago.

Change-Id: I2ddc26afc01edf84bb1bdb21a3488c88dd6c9775
Reviewed-on: http://gerrit.openafs.org/10318
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>