aklog: Only try to use krb5-weak.conf if it exists

The logic we use for using krb5-weak.conf to allow 'weak crypto'
requires us to know where the default krb5.conf is. The default
krb5.conf local can vary significantly depending on the platform, and
we don't have a good way of figuring out what it is, so we guess. We
may guess wrong.

To limit the cases where we guess wrong, only try to do this
workaround if the krb5-weak.conf file actually exists.

Change-Id: Id3905268b5cc22dafb4dd539b9f3d323a656fee2
Reviewed-on: http://gerrit.openafs.org/9667
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
volser: Indicate busy volume with VBUSY

Commit 34fc86bcc749f3bd059831b7e5dae03dc09a9393 changed several uses
of VBUSY to VOLSERVOLBUSY in order to detect retriable operations.
However, one such change did not change an Rx abort code, but instead
was used for the 'status' field for a volintInfo or volintXInfo
structure. That is not really a general error code, but a field with a
few specific known values (at least, that is how existing clients
interpret it).

Go back to using VBUSY, so clients indicate the volume as busy,
instead of as offline/unattached.

Reported by Andy Malato.

Change-Id: Ia569633d98266cb15c059e66150d8d7f91d20dca
Reviewed-on: http://gerrit.openafs.org/9678
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>