fix single-quote+ParseEnv bug

Fixes issues with parsing shell lines with single quotes used to group
things (eg. subshell calls).

Fix was to set `got` state to `argQuoted` as the double quote path used
(and which worked for it).

shellwords.go

@@ -232,7 +232,7 @@ loop:
 		case '\'':
 			if !doubleQuoted && !dollarQuote {
 				if singleQuoted {
-					got = argSingle
+					got = argQuoted
 				}
 				singleQuoted = !singleQuoted
 				continue