Rewrote image search

This code is more generic and support all cases. Previously
we had bug where the user lost his image path if the image
was not located in image directory.

gns3server/modules/iou/__init__.py

@@ -91,3 +91,9 @@ class IOU(BaseManager):
         """
 
         return os.path.join("iou", "device-{}".format(legacy_vm_id))
+
+    def get_images_directory(self):
+        """
+        Return the full path of the images directory on disk
+        """
+        return os.path.join(os.path.expanduser(self.config.get_section_config("Server").get("images_path", "~/GNS3/images")), "IOU")

gns3server/modules/iou/iou_vm.py

@@ -145,14 +145,7 @@ class IOUVM(BaseVM):
         :param path: path to the IOU image executable
         """
 
-        if not os.path.isabs(path):
-            server_config = self.manager.config.get_section_config("Server")
-            relative_path = os.path.join(os.path.expanduser(server_config.get("images_path", "~/GNS3/images")), path)
-            if not os.path.exists(relative_path):
-                relative_path = os.path.join(os.path.expanduser(server_config.get("images_path", "~/GNS3/images")), "IOU", path)
-            path = relative_path
-
-        self._path = path
+        self._path = self.manager.get_abs_image_path(path)
 
         # In 1.2 users uploaded images to the images roots
         # after the migration their images are inside images/IOU
@@ -240,11 +233,7 @@ class IOUVM(BaseVM):
                        "iourc_path": self.iourc_path}
 
         # return the relative path if the IOU image is in the images_path directory
-        server_config = self.manager.config.get_section_config("Server")
-        relative_image = os.path.join(os.path.expanduser(server_config.get("images_path", "~/GNS3/images")), "IOU", self.path)
-        if os.path.exists(relative_image):
-            iou_vm_info["path"] = os.path.basename(self.path)
-
+        iou_vm_info["path"] = self.manager.get_relative_image_path(self.path)
         return iou_vm_info
 
     @property