Really fuzz isc_lex_getmastertoken() in the test

Really fuzz isc_lex_getmastertoken() in the test

There was a copy&paste error in fuzz/isc_lex_getmastertoken.c where we
didn't really test the function we wanted to test.  Update the test to
have the input data to always include expected 'tokentype' in the first
byte, `eol` argument in the second byte and the rest of the input is the
data to parse.