pcsc: don't assume opts.pcsc_shared is present

Fixes running contrib/sim-rest-server.py:
  builtins.AttributeError: 'Namespace' object has no attribute 'pcsc_shared'

Change-Id: I864f65849c5d43cf7c73e60f1935afdf4273f696

pySim/transport/pcsc.py

@@ -57,7 +57,7 @@ class PcscSimLink(LinkBase):
                 raise ReaderError('No matching reader found for regex %s' % opts.pcsc_regex)
 
         self._con = self._reader.createConnection()
-        if not opts.pcsc_shared:
+        if not getattr(opts, "pcsc_shared", False):
             self._con = ExclusiveConnectCardConnection(self._con)
 
     def __del__(self):