chunkfs: call vfs clear_inode() from sops->evict_inode()

Because evict() (inode.c) didn't cal clear_inode() if
sops->evict_inode() is installed.
chunkfs: we can now use generic_shutdown_super() to clear all stuff

After 2a5d67e468b4300acbfb38433f34247eafb419f3 ("chunkfs: call vfs
clear_inode() from sops->evict_inode()") we can safely call
generic_shutdown_super() from kill super to avoid leaking of unfreed
inodes and other resources.

Since mentioned patch fix BUG that tirggered before, while
generic_shutdown_super() is called:
[ 1562.529605] ------------[ cut here ]------------
[ 1562.531578] kernel BUG at fs/inode.c:565!
[ 1562.532063] invalid opcode: 0000 [#2] PREEMPT SMP
[ 1562.532063] Modules linked in: chunkfs(O) loop fuse joydev hid_generic usbhid hid snd_pcm ohci_pci ohci_hcd snd_page_alloc ehci_hcd snd_timer snd usbcore soundcore psmouse evdev serio_raw pcspkr microcode parport_pc parport usb_common processor ac button thermal_sys i2c_piix4 i2c_core ext4 crc16 jbd2 mbcache sd_mod sg crc_t10dif sr_mod crct10dif_common cdrom ata_generic ahci libahci ata_piix libata scsi_mod e1000
[ 1562.532063] CPU: 0 PID: 3135 Comm: umount Tainted: G      D    O 3.13.0-rc7+ #98
[ 1562.532063] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[ 1562.532063] task: ffff88007c974860 ti: ffff88007b620000 task.ti: ffff88007b620000
[ 1562.532063] RIP: 0010:[<ffffffff8113a0f2>]  [<ffffffff8113a0f2>] evict+0x141/0x15a
[ 1562.532063] RSP: 0018:ffff88007b621d78  EFLAGS: 00010283
[ 1562.532063] RAX: ffff88007ffd0f08 RBX: ffff88007c4bb018 RCX: 0000000000000034
[ 1562.532063] RDX: 0000000000000003 RSI: ffff88007c4bb0b8 RDI: ffff88007ffd0f00
[ 1562.532063] RBP: ffff88007b621d90 R08: 0000000000000004 R09: ffff8800000b92c0
[ 1562.532063] R10: 817fade30000a5c8 R11: 0000000000000000 R12: ffff88007c4bb0a0
[ 1562.532063] R13: ffffffffa0284040 R14: ffffffffa0284040 R15: ffff88007cad9e80
[ 1562.532063] FS:  00007f2aa128c840(0000) GS:ffff88007fc00000(0000) knlGS:0000000000000000
[ 1562.532063] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 1562.532063] CR2: 0000000000405c60 CR3: 00000000374f6000 CR4: 00000000000006f0
[ 1562.532063] Stack:
[ 1562.532063]  ffff88007c4bb018 ffff88007c4bb0a0 ffff88007bfb8000 ffff88007b621dc0
[ 1562.532063]  ffffffff8113a64f ffff88007c4b5390 0000000000000000 ffff88007c4bb018
[ 1562.532063]  ffff88007c4b53e8 ffff88007b621df0 ffffffff81136a72 ffff88007c4b5390
[ 1562.532063] Call Trace:
[ 1562.532063]  [<ffffffff8113a64f>] iput+0x124/0x12d
[ 1562.532063]  [<ffffffff81136a72>] dentry_kill+0x18a/0x1e7
[ 1562.532063]  [<ffffffff81136bbd>] dput+0xee/0xfb
[ 1562.532063]  [<ffffffff811379e9>] shrink_dcache_for_umount+0x92/0xff
[ 1562.532063]  [<ffffffff811271d5>] generic_shutdown_super+0x1c/0xe8
[ 1562.532063]  [<ffffffffa0280022>] chunkfs_kill_super+0x22/0x65 [chunkfs]
[ 1562.532063]  [<ffffffff81127608>] deactivate_locked_super+0x27/0x48
[ 1562.532063]  [<ffffffff81127ac5>] deactivate_super+0x31/0x34
[ 1562.532063]  [<ffffffff8113d8ed>] mntput_no_expire+0x106/0x126
[ 1562.532063]  [<ffffffff8113e77e>] SYSC_umount+0x2d5/0x2f6
[ 1562.532063]  [<ffffffff81049ca0>] ? __set_current_blocked+0x44/0x49
[ 1562.532063]  [<ffffffff8113e89c>] SyS_umount+0x9/0xb
[ 1562.532063]  [<ffffffff813c97e2>] system_call_fastpath+0x16/0x1b
[ 1562.532063] Code: ff 4c 8d a3 88 00 00 00 4c 89 e7 e8 64 9c 28 00 48 8d bb a0 00 00 00 be 03 00 00 00 e8 9f fb f2 ff 48 83 bb a0 00 00 00 60 74 02 <0f> 0b 4c 89 e7 e8 65 99 28 00 48 89 df e8 d6 f9 ff ff 5b 41 5c
[ 1562.532063] RIP  [<ffffffff8113a0f2>] evict+0x141/0x15a
[ 1562.532063]  RSP <ffff88007b621d78>
[ 1562.574530] ---[ end trace 92c6c2712d73b54e ]---
[ 1562.575038] BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:20
[ 1562.575910] in_atomic(): 1, irqs_disabled(): 0, pid: 3135, name: umount
[ 1562.577003] CPU: 0 PID: 3135 Comm: umount Tainted: G      D    O 3.13.0-rc7+ #98
[ 1562.577837] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[ 1562.578704]  0000000000000000 ffff88007b621a90 ffffffff813bf56e ffff88007c974860
[ 1562.579907]  ffff88007b621ab0 ffffffff8105dfee ffff88007a29daa0 000000000000000b
[ 1562.581179]  ffff88007b621ac8 ffffffff813c2f08 ffff88007c974860 ffff88007b621af0
[ 1562.582468] Call Trace:
[ 1562.582897]  [<ffffffff813bf56e>] dump_stack+0x4e/0x7a
[ 1562.583428]  [<ffffffff8105dfee>] __might_sleep+0xf1/0xf6
[ 1562.583962]  [<ffffffff813c2f08>] down_read+0x1b/0x2c
[ 1562.585549]  [<ffffffff81049b46>] exit_signals+0x1e/0x10b
[ 1562.586091]  [<ffffffff8103c6d0>] do_exit+0x119/0x933
[ 1562.586610]  [<ffffffff813bd2b5>] ? printk+0x62/0x64
[ 1562.587130]  [<ffffffff8107736d>] ? kmsg_dump+0xa4/0xaa
[ 1562.587654]  [<ffffffff813c4d0f>] oops_end+0xa1/0xa8
[ 1562.588134]  [<ffffffff81004fb3>] die+0x55/0x5e
[ 1562.588593]  [<ffffffff813c47bc>] do_trap+0x65/0x12a
[ 1562.589113]  [<ffffffff81002bad>] do_invalid_op+0x93/0x9c
[ 1562.589642]  [<ffffffff8113a0f2>] ? evict+0x141/0x15a
[ 1562.590167]  [<ffffffff81076201>] ? console_unlock+0x2de/0x2fc
[ 1562.590712]  [<ffffffff813cacc8>] invalid_op+0x18/0x20
[ 1562.591234]  [<ffffffff8113a0f2>] ? evict+0x141/0x15a
[ 1562.591756]  [<ffffffff8113a0e8>] ? evict+0x137/0x15a
[ 1562.592231]  [<ffffffff8113a64f>] iput+0x124/0x12d
[ 1562.592542]  [<ffffffff81136a72>] dentry_kill+0x18a/0x1e7