This issue is not seen on 3.7.9-10.el7rhgs.x86_64. 

Here are the steps which were followed,

1.Created a distribute volume with 4 bricks and started it.
2.NFS mount the volume and created some files 
for i in {1..500} ; do dd if=/dev/urandom of=f"$i" bs=10M count=1; done
3.Calculated are-equal check sum on mount point before starting rebalance.
4.Added a brick and start rebalance 
5. While rebalance is in-progress, renamed some files. 
6. After rebalance is completed, calculated the are-equal checksum on the mount point. 

The file count remains same before and after the rebalance.

Also, while rebalance is in-progress renaming of files is failing with an error 'No such file or directory' even though files are present. This is a different issue and is being tracked with 1286127.

Thanks Prasad.

I am closing this BZ based on comment#4.