Fix dropwizard parsing error for metrics that need escaped (#4142)

If the dropwizard parser cannot convert the metric name into a valid
line protocol series then we will accept the name as is.

(cherry picked from commit 0af40a8a5d)

plugins/parsers/influx/machine_test.go

@@ -1390,3 +1390,80 @@ func BenchmarkMachineProcstat(b *testing.B) {
 		}
 	}
 }
+
+func TestSeriesMachine(t *testing.T) {
+	var tests = []struct {
+		name    string
+		input   []byte
+		results []Result
+		err     error
+	}{
+		{
+			name:    "empty string",
+			input:   []byte(""),
+			results: nil,
+		},
+		{
+			name:  "no tags",
+			input: []byte("cpu"),
+			results: []Result{
+				Result{
+					Name:  Measurement,
+					Value: []byte("cpu"),
+				},
+			},
+		},
+		{
+			name:  "tags",
+			input: []byte("cpu,a=x,b=y"),
+			results: []Result{
+				Result{
+					Name:  Measurement,
+					Value: []byte("cpu"),
+				},
+				Result{
+					Name:  TagKey,
+					Value: []byte("a"),
+				},
+				Result{
+					Name:  TagValue,
+					Value: []byte("x"),
+				},
+				Result{
+					Name:  TagKey,
+					Value: []byte("b"),
+				},
+				Result{
+					Name:  TagValue,
+					Value: []byte("y"),
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			handler := &TestingHandler{}
+			fsm := NewSeriesMachine(handler)
+			fsm.SetData(tt.input)
+
+			count := 0
+			for fsm.ParseLine() {
+				if fsm.Err() != nil {
+					handler.AddError(fsm.Err())
+				}
+				count++
+				if count > 20 {
+					break
+				}
+			}
+
+			if fsm.Err() != nil {
+				handler.AddError(fsm.Err())
+			}
+
+			results := handler.Results()
+			require.Equal(t, tt.results, results)
+		})
+	}
+}