autotest: Fix kernel module unit test teardown

autotest: Fix kernel module unit test teardown

Due to a misnaming, the macro calls

  OVS_SWITCHD_STOP([$1])
  AT_CHECK([modprobe -r openvswitch])

in OVS_KMOD_VSWITCHD_STOP make up a syntactically correct function definition
(OVS_SWITCHD_STOP does not exist, and therefore the call does not expand):

  OVS_SWITCHD_STOP()
  { set +x
  $as_echo "$at_srcdir/kmod-traffic.at:15: modprobe -r openvswitch"
  ...
  $at_traceon; }

Consequently, neither of the calls has the intended effect, i.e., stopping
ovs-vswitchd and ovsdb-server, checking their log files, and unloading the
datapath kernel module. Fix the misnaming, so all calls expand properly.

Fixes: 69c2bdfef9 ("autotest: add autotest framework for adding kernel module unit tests")
Signed-off-by: Christoph Jaeger <cj@linux.com>
Signed-off-by: Andy Zhou <azhou@nicira.com>
Author: add Christoph Jaeger