control-files will always start with 'cfA*'. It turns out that some
implementations of lpd (such as solaris) may send a control file which
starts with 'cfB*', or really 'cf<anyLetter>*'. Although such filenames
are very odd, we did used to accept them. This changes ctl_renametf to
work correctly with them, and fixes up 'lpc clean' to match.
PR: bin/32183
MFC after: 10 days