The new code is dedicated to calculate free inodes number of all inode_allocs,
then return the info to userpace in terms of an array.

Specially, flag 'OCFS2_INFO_FL_NON_COHERENT', manipulated by '--cluster-coherent'
from userspace, is now going to be involved. setting the flag on means no cluster
coherency considered, usually, userspace tools choose none-coherency strategy by
default for the sake of performace.
Signed-off-by: NTristan Ye <tristan.ye@oracle.com>