afscp: Fix -s option for writes

When writing to AFS with afscp, the -s option was sleeping before any
StoreData RPCs actually got issued to the fileserver. Move the sleep
to after we have done one rx_Read/rx_Write, so we sleep after starting
to contact the fileserver, to make sleeping while writing more
consistent with sleeping while reading.

Reviewed-on: http://gerrit.openafs.org/3762
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 380cc22a45dff7e40cd50d57a56742b59ccc4952)

Change-Id: I5bafad6958111bfb196adde79361939b00a176a1
Reviewed-on: http://gerrit.openafs.org/9417
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>