Improve doublecheck

= Revision 11732

= Issue Description Doublecheck feature in OSCam is almost unusable. There are many issues with it:

• lot of spam to log (I would prefer having global logs only when CW is invalid)
• can not recover itself if first CW was invalid (until another reader confirms invalid CW)
• corrupted CW goes to cache and other clients would get corrupted CW if asked for decode the same ECM (cache1)

This patch improves doublecheck so it starts to be usable:

• we store 2 CWs instead of 1, this allows to compare CW from 3rd reader
  • in case of 1 bad and 2 valid readers, doublecheck is able to detect and drop invalid CW correctly
    • unfortunately, marking bad reader in stats has not been implemented yet
  • in case of 2 bad readers we are not able to have any success (as doublecheck can not do magic)
• non-debug log is pushed when doublecheck detects bad CW
• we pause adding first CW to cache until we verify it
• we do not do doublecheck at all, if cw_cycle_check succeed (it always has priority as it runs before doublecheck)
• consider doublecheck as additional check for CWs that can not be checked by cw_cycle_check yet (like CWC LEARN)

= When the issue occurs Always when doublecheck was enabled

= How the issue is reproducable Connect readers producing fake CWs

= Possible effects Increased time reports for answers from cache1