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/base_manager.py

@@ -371,3 +371,40 @@ class BaseManager:
             nio = NIOGenericEthernet(nio_settings["ethernet_device"])
         assert nio is not None
         return nio
+
+    def get_abs_image_path(self, path):
+        """
+        Get the absolute path of an image
+
+        :param path: file path
+        :return: file path
+        """
+
+        img_directory = self.get_images_directory()
+
+        if not os.path.isabs(path):
+            s = os.path.split(path)
+            return os.path.normpath(os.path.join(img_directory, *s))
+        return path
+
+    def get_relative_image_path(self, path):
+        """
+        Get a path relative to images directory path
+        or an abspath if the path is not located inside
+        image directory
+
+        :param path: file path
+        :return: file path
+        """
+
+        img_directory = self.get_images_directory()
+        path = self.get_abs_image_path(path)
+        if os.path.dirname(path) == img_directory:
+            return os.path.basename(path)
+        return path
+
+    def get_images_directory(self):
+        """
+        Get the image directory on disk
+        """
+        raise NotImplementedError