LU-14965 ldiskfs: rhel7.6 inode mutex for ldiskfs_orphan_add

See following warning:

ldiskfs/namei.c:3331 ldiskfs_orphan_add+0x11e/0x290 [ldiskfs]
Call Trace:
	dump_stack+0x19/0x1b
	__warn+0xd8/0x100
	warn_slowpath_null+0x1d/0x20
	ldiskfs_orphan_add+0x11e/0x290 [ldiskfs]
	ldiskfs_xattr_inode_orphan_add+0xbb/0x110 [ldiskfs]
	ldiskfs_xattr_delete_inode+0x5c/0x350 [ldiskfs]
	ldiskfs_evict_inode+0x1a8/0x630 [ldiskfs]
	evict+0xb4/0x180
	iput+0xfc/0x190
	osd_object_delete+0x1f8/0x370 [osd_ldiskfs]
	lu_object_free.isra.27+0xb8/0x1c0 [obdclass]
	lu_object_put+0xa5/0x460 [obdclass]
	mdt_object_put+0x30/0x110 [mdt]
	mdt_reint_unlink+0x8e0/0x1890 [mdt]
	mdt_reint_rec+0x83/0x210 [mdt]
	mdt_reint_internal+0x720/0xaf0 [mdt]
	mdt_reint+0x67/0x140 [mdt]
	tgt_request_handle+0x7ea/0x1750 [ptlrpc]
	ptlrpc_server_handle_request+0x256/0xb10 [ptlrpc]
	ptlrpc_main+0xb3c/0x14e0 [ptlrpc]
	kthread+0xd1/0xe0
	ret_from_fork_nospec_begin+0x21/0x21

Need to hold inode mutex on the external EA for ldiskfs_orphan_add()
to soothe the warning.

This is a port of:

Lustre-commit: 7d3b5d9fdc766411eacaed27fb2fd9250800f096
Lustre-change: https://review.whamcloud.com/44754

Test-Parameters: trivial
Fixes: f64e9f19f68e ("LU-12977 ldiskfs: properly take inode_lock() for truncates")
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I47a01862793afaac1d7c311f1b6d65d2cf4bb93f
Reviewed-on: https://review.whamcloud.com/45165
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andrew Perepechko <andrew.perepechko@hpe.com>
Reviewed-by: Alexander Zarochentsev <alexander.zarochentsev@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>