Reject invalid flag combinations to avoid potential data corruption or
failing raid set construction:

 - add definitions for constructor flag combinations and invalid flags
   per level

 - add bool test functions for the various raid types
   (also will be used by future reshaping enhancements)

 - introduce rs_check_for_invalid_flags() and _invalid_flags()
   to perform the validity checks
Signed-off-by: NHeinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>