Fix panic when handling string fields with escapes (#3188)

internal/models/makemetric.go

@@ -150,12 +150,6 @@ func makemetric(
 				continue
 			}
 		case string:
-			if strings.HasSuffix(val, `\`) {
-				log.Printf("D! Measurement [%s] field [%s] has a value "+
-					"ending with a backslash, skipping", measurement, k)
-				delete(fields, k)
-				continue
-			}
 			fields[k] = v
 		default:
 			fields[k] = v

internal/models/running_input_test.go

@@ -370,16 +370,17 @@ func TestMakeMetric_TrailingSlash(t *testing.T) {
 			expectedTags: map[string]string{},
 		},
 		{
-			name:        "Field value with trailing slash dropped",
+			name:        "Field value with trailing slash okay",
 			measurement: `cpu`,
 			fields: map[string]interface{}{
 				"value": int64(42),
-				"bad":   `xyzzy\`,
+				"ok":    `xyzzy\`,
 			},
 			tags:                map[string]string{},
 			expectedMeasurement: `cpu`,
 			expectedFields: map[string]interface{}{
 				"value": int64(42),
+				"ok":    `xyzzy\`,
 			},
 			expectedTags: map[string]string{},
 		},
@@ -387,7 +388,7 @@ func TestMakeMetric_TrailingSlash(t *testing.T) {
 			name:        "Must have one field after dropped",
 			measurement: `cpu`,
 			fields: map[string]interface{}{
-				"bad": `xyzzy\`,
+				"bad": math.NaN(),
 			},
 			tags:        map[string]string{},
 			expectedNil: true,