Update test_services.py

Added tests for services.shutdown and services.shutdown

Tip: 
       self.assertNotEqual(None, svc.getConnectionCount())
       self.assertNotEqual(None, svc.getAttachedDatabaseNames())
       self.assertNotEqual(None, svc.getLog())

failed on Centos 5.3 Firebird 1.5  with error: 

F
======================================================================
FAIL: test_services (__main__.TestServices)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "./test_services.py", line 36, in test_services
    self.assertNotEqual(None, svc.getConnectionCount())
  File "/opt/python26/lib/python2.6/site-packages/firebirdsql/services.py", line 370, in getConnectionCount
    return self._getSvrDbInfo()[0]
  File "/opt/python26/lib/python2.6/site-packages/firebirdsql/services.py", line 313, in _getSvrDbInfo
    assert byte_to_int(buf[0]) == isc_info_svc_svr_db_info
AssertionError

----------------------------------------------------------------------
Ran 1 test in 0.060s

FAILED (failures=1)

With Centos 6.3 x86_64 Firebird 2.5.1 works fine, without any errors:

python2.6 ./test_services.py
.
----------------------------------------------------------------------
Ran 1 test in 0.149s

OK