partitioning: Add an empty mount point option

It's not obvious that the combo can be edited. Users need to be
able to remove an assigned mount point.

Author: clefebvre

usr/lib/live-installer/partitioning.py

@@ -627,7 +627,7 @@ def __init__(self, path, mount_as, format_as, type):
         # Build list of pre-provided mountpoints
         combobox = self.builder.get_object("comboboxentry_mount_point")
         model = Gtk.ListStore(str, str)
-        for i in ["/", "/home", "/boot", "/boot/efi", "/srv", "/tmp", "swap"]:
+        for i in ["", "/", "/home", "/boot", "/boot/efi", "/tmp", "swap"]:
             model.append(["", i])
         combobox.set_model(model)
         combobox.set_entry_text_column(1)