fix random file verifier with small files
fix random file verifier with small files

The file verifier will now correctly verify small files (smaller than
the md5 digest size), as long as the data that is there matches what
the digest would be.

Nexenta/s3-tests,Nexenta/s3-tests,andrewgaul/s3-tests,robbat2/s3-tests,robbat2/s3-tests,smithfarm/s3-tests,timuralp/s3-tests,dreamhost/s3-tests,Nexenta/s3-tests,Intel-bigdata/s3-tests,Nexenta/s3-tests,SUSE/s3-tests,dreamhost/s3-tests,timuralp/s3-tests,andrewgaul/s3-tests,jmunhoz/s3-tests,ceph/s3-tests,tobegit3hub/s3-tests,smithfarm/s3-tests,tobegit3hub/s3-tests,ceph/s3-tests,piousbox/s3-tests,Intel-bigdata/s3-tests,basho/s3-tests,piousbox/s3-tests,jmunhoz/s3-tests,basho/s3-tests,piousbox/s3-tests,SUSE/s3-tests