remove obsolete md5 import.

md5 is deprecated since 2.5 and we need py version 2.6.5 or higher
for core. On the other hand md5 isn't use at site.py. I removed it
and opened bug 65760 to fix if needed.

Change-Id: Ifdc0e07f90c842f33139fb45875d1a07ce8240cf
Merge "remove obsolete md5 import."