ceph: add missing init_acl() for mkdir() and atomic_open()

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
ceph: fix ceph_set_acl()

If acl is equivalent to file mode permission bits, ceph_set_acl()
needs to remove any existing acl xattr. Use __ceph_setxattr() to
handle both setting and removing acl xattr cases, it doesn't return
-ENODATA when there is no acl xattr.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
ceph: fix __dcache_readdir()

If directory is fragmented, readdir() read its dirfrags one by one.
After reading all dirfrags, the corresponding dentries are sorted in
(frag_t, off) order in the dcache. If dentries of a directory are all
cached, __dcache_readdir() can use the cached dentries to satisfy
readdir syscall. But when checking if a given dentry is after the
position of readdir, __dcache_readdir() compares numerical value of
frag_t directly. This is wrong, it should use ceph_frag_compare().

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>