fs/manifest.go: mkDirPath(): skip empty path elements

When the path string supplied to mkDirPath() has sequences of
consecutive '/' characters, or is empty (which can happen during
`ops pkg load` command execution), the filesystem code was creating
tuple attributes with emtpy symbols, which are useless.
This commit fixes it.

fs/manifest.go

@@ -521,11 +521,11 @@ func (m *Manifest) MkdirPath(path string) {
 }
 
 func mkDirPath(parent map[string]interface{}, path string) map[string]interface{} {
-	path = strings.TrimPrefix(path, "/")
-	path = strings.TrimSuffix(path, "/")
 	parts := strings.Split(path, "/")
 	for _, element := range parts {
-		parent = mkDir(parent, element)
+		if element != "" {
+			parent = mkDir(parent, element)
+		}
 	}
 	return parent
 }