MFC r293878,r293880,r295116,r295117,r295477:

r293878:

Remove unnecessary kldload logic added to geom_subr.sh in r293028

r293880:

PID file support hasn't been committed for ggated(8) yet. Unbreak running
the testcase more than once by restoring the "killall ggated"

r295116:

Add an additional 1 second sleep to after calling ggatec before calling
dd to defeat a race when writing out to the geom_gate(4) device

This will quell the Jenkins failure emails until I come up with a better
solution

r295117:

Use the pidfile support added to ggated(8) in r294973 to ensure that the
ggated(8) daemon used by the tests is the instance specifically invoked by
the tests instead of one or more daemon instances running on the system

r295477:

Similar to r295116, add an additional 1 second sleep after calling ggatel
before calling dd to defeat a race when writing out to the geom_gate(4)
device