test: add helper function to wait until file is created

Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: Ib706727c680471334b90960148ee1a637561cf64

Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/452805
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

@@ -675,6 +675,22 @@ function waitforblk_disconnect()
 	return 0
 }
 
+function waitforfile()
+{
+	local i=0
+	while [ ! -f $1 ]; do
+		[ $i -lt 200 ] || break
+		i=$[$i+1]
+		sleep 0.1
+	done
+
+	if [ ! -f $1 ]; then
+		return 1
+	fi
+
+	return 0
+}
+
 function fio_config_gen()
 {
 	local config_file=$1