ocfs2: add dlm_recover_callback_support in sysfs

ocfs2: add dlm_recover_callback_support in sysfs

This is a part of the nocontrold feature which was incorporated sometime
back.

This is required for backward compatibility of the tools, specifically
the scenario where the tools with recovery callback is used with a
kernel not using the recovery callbacks (older kernel + newer tools).
The tools look for this file to understand if the kernel supports DLM
recovery callbacks.

For kernels which support recovery callbacks but will miss this patch,
ocfs2 will continue to use the older API and would still be able to
mount the filesystem.

[[email protected]: simplify]
[[email protected]: VERIFY_OCTAL_PERMISSIONS fix up]
Signed-off-by: Goldwyn Rodrigues <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Signed-off-by: Stephen Rothwell <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>