LP#1243841: quiet a misleading indentation warning

LP#1243841: quiet a misleading indentation warning

Adjusts a spaces-vs-tabs issue to fix the following compilation
warning:

osrf_prefork.c: In function ‘check_children’:
osrf_prefork.c:1067:5: warning: this ‘if’ clause does not
guard... [-Wmisleading-indentation]
     if( select_ret <= 0 ) // we're done here
     ^~
osrf_prefork.c:1072:2: note: ...this statement, but the latter is
misleadingly indented as if it is guarded by the ‘if’
  cur_child = forker->first_child;
  ^~~~~~~~~

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>