filesystem: fix typo in method call app()->append()

In the method add_application() the method name should be append()
instead of add().

Change-Id: Ic8ad62567968e09786eac86f219b56a3d3200511
Related: OS#4963

pySim/filesystem.py

@@ -713,7 +713,7 @@ class CardProfile(object):
         return self.name
 
     def add_application(self, app):
-        self.applications.add(app)
+        self.applications.append(app)
 
     def interpret_sw(self, sw):
         """Interpret a given status word within the profile.  Returns tuple of