fix-configure-after-scan:

Some refactoring of the Configure method to resolve the
bug of configuration failure after and EndScan command:
- if subarray is READY when Configure is issued, put a delay to wait
  for CONFIGURING transition (temporary hack)
- added check on scan configuration string: if is equal to the
  last valid configuration programmed, the configuration step is
  skipped (the subarray is already programmed)
- if failure/timeout during configuration, check if the failed
  device is the CBF subarray.
- decorators for Configure method are applied in the mid/low instance
  code.
Updated the tests.