DBBC3 comm error disables multicast time-out error

[wehimwich]

@jfhquick noted that an error from the DBBC3 for an unknown command disables the multicast time-out error. This can be elicited with, e.g., dbbc3=junk.

This is caused because the logic for disabling the multicast time-out error for a DBBC3 communication in dbbcn does not get reset when an error occurs. Basically, only the normal exit is covered, not the error exit. The next successful DBBC3 communication would reenable the multicast time-out error. This will be fixed so that the time-out error doesn't get disabled in any case.