smurf: Fix bug that caused creation of shortmaps or bolomaps to segfault

Since commit e93e76879e7, smf_rebinmap1 has required a separate map for
each thread. The routines for writing short maps and bolo maps do not yet
support this, so ensure smf_rebinmap1 is called with no workforce. Some
day, when there is nothing more important to do, we could change this to
allow multi-threaded creation of short maps and bolo maps.