wsl: tidy wsl-fix-interop

wsl/scripts/wsl-fix-interop

@@ -1,4 +1,6 @@
 (return 0 2>/dev/null) || { >&2 echo This script must be sourced, not run directly.; exit 1; }
-for i in $(pstree --numeric-sort --show-parents --show-pids $$ | grep --extended-regexp --only-matching '[0-9]+'); do
-	[ -e /run/WSL/${i}_interop ] && export WSL_INTEROP=/run/WSL/${i}_interop
+for pid in $(pstree --numeric-sort --show-parents --show-pids $$ | grep --extended-regexp --only-matching '[0-9]+'); do
+	if [ -S /run/WSL/${pid}_interop ]; then
+		WSL_INTEROP=/run/WSL/${pid}_interop
+	fi
 done