filer.backup: escape colon from path on windows

fix https://github.com/chrislusf/seaweedfs/issues/2084

weed/command/filer_sync_windows.go

@@ -0,0 +1,12 @@
+package command
+
+import (
+	"strings"
+)
+
+func escapeKey(key string) string {
+	if strings.Contains(key, ":") {
+		return strings.ReplaceAll(key, ":", "")
+	}
+	return key
+}