viced: Add options for interrupting clients

viced: Add options for interrupting clients

Add the -offline-timeout and -offline-shutdown-timeout options to the
fileserver, to implement interrupting clients accessing volumes we are
trying to take the volume offline. Document the new options.

Currently this is only implemented for read operations. Implementing
this for write operations and callback breaks will require more work.

This also removes the VGetVolumeTimed interface from the volume
package, since the fileserver was the only user and with this change
the fileserver now uses the VGetVolumeWithCall interface.

Change-Id: I2c6246d522d37dfd2fa0ecf69d6f71803b2acc03
Reviewed-on: http://gerrit.openafs.org/2984
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>