autotest.sh: changed to accomodate agents with no nvme devices.

Change-Id: I0098cad19e3b8492495d0e779fd2bc52ef1bf23b
Signed-off-by: Seth Howell <seth.howell@intel.com>
Reviewed-on: https://review.gerrithub.io/363125
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

autotest.sh

@@ -50,7 +50,7 @@ if [ $(uname -s) = Linux ]; then
 	sleep 10
 
 	# Delete all partitions on NVMe devices
-	devs=`lsblk -l -o NAME | grep nvme | grep -v p`
+	devs=`lsblk -l -o NAME | grep nvme | grep -v p` || true
 	for dev in $devs; do
 		parted -s /dev/$dev mklabel msdos
 	done