imaging: Refs #2191 Traceback when associate imaging

When associating imaging server with other entity than UUID1 (who comes
with imaging SQL schemas), english default language cannot be set.

And a traceback is born...

This commit fixes it
glpi: Fix traceback on getLocationName method

getLocationName uuid param is not always a list, it is called with a
string on imaging main page
glpi: Fix getLocationParentPath traceback

If fake root entity is selected, available imaging server are not
displayed on main imaging page