test/autotest_common: add new function waitforbdev()

Waits up to 2 seconds for a bdev to arrive, if not returns error.
In the next patch in this series this is used and seems like a good
general function.

Change-Id: I3402f34f3dad3d7373973dc785520a5c4e58cd14
Signed-off-by: paul luse <paul.e.luse@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/456091
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>

test/common/autotest_common.sh

@@ -416,6 +416,21 @@ function waitfornbd() {
 	return 1
 }
 
+function waitforbdev() {
+	local bdev_name=$1
+	local i
+
+	for ((i=1; i<=20; i++)); do
+		if ! $rpc_py get_bdevs | jq -r '.[] .name' | grep -qw $bdev_name; then
+			sleep 0.1
+		else
+			return 0
+		fi
+	done
+
+	return 1
+}
+
 function killprocess() {
 	# $1 = process pid
 	if [ -z "$1" ]; then