Moving drop code into dbschem.py

 - Use py.test rather than nosetests in cronjob
 - Updating select statements to not use wildcards
 - Add ttypes to checkables in dbschem.py
 - Moved the code to drop test tables into dbschem and consolidated it so all
   the lookups and drops can be done through a single database connection
   (rather than a separate connection for each drop)

Change-Id: I6ca39cf51b46765d7ac5c7c5aafe029617efc714
Desupporting wildcard selects as bad practice

 - Updated DBI test routines to expect a DBIerror when fields is empty or
   unspecified
 - Updated DBI.select() routines to satisfy the tests
 - Remove code from DBI.select() that would put the '*' in select
 - Added field list to select statements that were missing one

Change-Id: I1df67c20a247e1fd9d0ab83942e2843feaa5cada
Skip hpss tests when HSI is not available

 - Corrected several exception tests to use self.assertRaisesMsg()

Change-Id: I762f5e6c8a5969f2d09a277e52f1e55b81bb8909