Fix spelling error (retreive for retrieve) in strings

Caught by Lintian analysis of the compiled binaries.

Reviewed-on: http://gerrit.openafs.org/8865
Reviewed-by: Ken Dreyer <ktdreyer@ktdreyer.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 2e5ef04e24c89e846af7aae7da57a0b0f5e200c3)

Change-Id: I3ae8b3c4bed7197e19667c34d93c933d1047efd1
Reviewed-on: http://gerrit.openafs.org/8932
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>