ocfs2: Support commit= mount option

ocfs2: Support commit= mount option

Mostly taken from ext3. This allows the user to set the jbd commit interval,
in seconds. The default of 5 seconds stays the same, but now users can
easily increase the commit interval. Typically, this would be increased in
order to benefit performance at the expense of data-safety.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>