add option to truncate cache table during startup for bvfs_test
add option to truncate cache table during startup for bvfs_test

rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula,rkorzeniewski/bacula