filesystem: fix reset mechanism

Currently we call the reset_card and get_atr methods directly at the
transport layer via the private _scc and _tp object of the card. This is
a violation. Fix and use the reset methods that are already in the
SimCard object.

Change-Id: I0e9d2a62a42a7387e7ca69d2ae830782a61aed89
diff --git a/pySim/filesystem.py b/pySim/filesystem.py
index cc9176f..dcc2608 100644
--- a/pySim/filesystem.py
+++ b/pySim/filesystem.py
@@ -1068,8 +1068,7 @@
         Args:
             cmd_app : Command Application State (for unregistering old file commands)
         """
-        self.card._scc._tp.reset_card()
-        atr = i2h(self.card._scc._tp.get_atr())
+        atr = i2h(self.card.reset())
         # select MF to reset internal state and to verify card really works
         self.select('MF', cmd_app)
         return atr