Fix zfs_destroy_001_pos.ksh

Due to how the Linux VFS was designed busy mount points
cannot be destroyed even when given the force option. Update
the zfs_destroy_001_pos test case to expect this behavior when
running under Linux.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: candychencan <chen.can2@zte.com.cn>
Closes #5132