Change cache_inode_readdir_cb_t and handle_digest obj_handle to const

Signed-off-by: Amit Dror <amitd@infinidat.com>

Conflicts:
	src/FSAL/FSAL_GPFS/handle.c
	src/FSAL/FSAL_LUSTRE/handle.c
	src/FSAL/FSAL_POSIX/handle.c
	src/FSAL/FSAL_PROXY/handle.c
	src/FSAL/FSAL_VFS/handle.c
	src/FSAL/FSAL_ZFS/handle.c
	src/include/nfs_file_handle.h

Signed-off-by: Matt Benjamin <matt@linuxbox.com>
Remove redundant handle_to_key() call in cache_inode_kill_entry()

Signed-off-by: Amit Dror <amitd@infinidat.com>
Signed-off-by: Matt Benjamin <matt@linuxbox.com>
Remove associated option from cache_inode_get()

It is no longer used by cache_inode_lookupp_impl()

Signed-off-by: Amit Dror <amitd@infinidat.com>

Conflicts:
	src/support/nfs_filehandle_mgmt.c

Signed-off-by: Matt Benjamin <matt@linuxbox.com>