autotest_common: add waitforblk_disconnect

This is the functional opposite of waitforblk.

Change-Id: I5e9f77c9ea05b83b8dbfbf49bb3baa2ae8cc1086
Signed-off-by: Seth Howell <seth.howell@intel.com>
Reviewed-on: https://review.gerrithub.io/c/443316
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>

test/common/autotest_common.sh

@@ -657,6 +657,22 @@ function waitforblk()
 	return 0
 }
 
+function waitforblk_disconnect()
+{
+	local i=0
+	while lsblk -l -o NAME | grep -q -w $1; do
+		[ $i -lt 15 ] || break
+		i=$[$i+1]
+		sleep 1
+	done
+
+	if lsblk -l -o NAME | grep -q -w $1; then
+		return 1
+	fi
+
+	return 0
+}
+
 function fio_config_gen()
 {
 	local config_file=$1