Update zfs_mount_005_pos.ksh and zfs_mount_010_neg.ksh

Update zfs_mount_005_pos.ksh and zfs_mount_010_neg.ksh to reflect
the expected Linux behavior. The is_linux wrapper is used so the
test case may be used on Linux and non-Linux platforms.

Signed-off-by: liuhuang <liu.huang@zte.com.cn>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #5000