app/vminsert/influx: do not allow escaping newline char, since they dont occur in real life

The prefious report with escaped newline chars in influx line protocol was false alarm.

app/vminsert/influx/parser.go

@@ -180,7 +180,7 @@ func (f *Field) unmarshal(s string, noEscapeChars, hasQuotedFields bool) error {
 func unmarshalRows(dst []Row, s string, tagsPool []Tag, fieldsPool []Field) ([]Row, []Tag, []Field, error) {
 	noEscapeChars := strings.IndexByte(s, '\\') < 0
 	for len(s) > 0 {
-		n := nextUnquotedChar(s, '\n', noEscapeChars, true)
+		n := strings.IndexByte(s, '\n')
 		if n == 0 {
 			// Skip empty line
 			s = s[1:]
@@ -291,7 +291,7 @@ func unescapeTagValue(s string, noEscapeChars bool) string {
 			return string(append(dst, '\\'))
 		}
 		ch := s[0]
-		if ch != ' ' && ch != ',' && ch != '=' && ch != '\\' && ch != '\n' {
+		if ch != ' ' && ch != ',' && ch != '=' && ch != '\\' {
 			dst = append(dst, '\\')
 		}
 		dst = append(dst, ch)

app/vminsert/influx/parser_test.go

@@ -324,11 +324,11 @@ func TestRowsUnmarshalSuccess(t *testing.T) {
 	})
 
 	// Escape chars
-	f(`fo\,bar\=baz,x\==\\a\,\=\q\  \\\a\=\,=4.34`, &Rows{
+	f(`fo\,bar\=baz,x\=\b=\\a\,\=\q\  \\\a\=\,=4.34`, &Rows{
 		Rows: []Row{{
 			Measurement: `fo,bar=baz`,
 			Tags: []Tag{{
-				Key:   `x=`,
+				Key:   `x=\b`,
 				Value: `\a,=\q `,
 			}},
 			Fields: []Field{{
@@ -338,27 +338,6 @@ func TestRowsUnmarshalSuccess(t *testing.T) {
 		}},
 	})
 
-	// Escape newline
-	f("fo\\\nb\\,ar,x\\\ny=\\\n\\y a=\"foo\nbar\",b\\\nc\\==34\n", &Rows{
-		Rows: []Row{{
-			Measurement: "fo\nb,ar",
-			Tags: []Tag{{
-				Key:   "x\ny",
-				Value: "\n\\y",
-			}},
-			Fields: []Field{
-				{
-					Key:   "a",
-					Value: 0,
-				},
-				{
-					Key:   "b\nc=",
-					Value: 34,
-				},
-			},
-		}},
-	})
-
 	// Multiple lines
 	f("foo,tag=xyz field=1.23 48934\n"+
 		"bar x=-1i\n\n", &Rows{