common/rc: Fix fcollapse require code to work with 64k block size

common/rc: Fix fcollapse require code to work with 64k block size

For 64k block size, the require code fails because the block range
[4k, 12k] would cause the fcollapse syscall to return -EINVAL. Hence
the tests using them are not executed.

This commit fixes the issue by calculating file offset ranges based
on the block size of the underlying filesystem.

Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>