inputs.x509_cert: Try to use globpath only on all file://, / sources

(not on sources starting with <driveletter>:\)
See: influxdata#9289 for more information.

plugins/inputs/x509_cert/x509_cert.go

@@ -66,20 +66,21 @@ func (c *X509Cert) SampleConfig() string {
 func (c *X509Cert) sourcesToURLs() error {
 	for _, source := range c.Sources {
 		if strings.HasPrefix(source, "file://") ||
-			strings.HasPrefix(source, "/") ||
-			strings.Index(source, ":\\") == 1 {
+			strings.HasPrefix(source, "/") {
 			source = filepath.ToSlash(strings.TrimPrefix(source, "file://"))
 			g, err := globpath.Compile(source)
 			if err != nil {
 				return fmt.Errorf("could not compile glob %v: %v", source, err)
 			}
 			c.globpaths = append(c.globpaths, g)
 		} else {
+			if strings.Index(source, ":\\") == 1 {
+				source = "file://" + filepath.ToSlash(source)
+			}
 			u, err := url.Parse(source)
 			if err != nil {
 				return fmt.Errorf("failed to parse cert location - %s", err.Error())
 			}
-
 			c.locations = append(c.locations, u)
 		}
 	}