Set the timezone to PDT.

Following the instructions here:
   http://serverfault.com/questions/84521/automate-dpkg-reconfigure-tzdata/84528#84528

cf.
   http://stackoverflow.com/questions/11931566/how-to-set-the-time-zone-in-amazon-ec2
   http://stackoverflow.com/questions/8777111/jenkins-show-wrong-time

Auditors: chris

Test Plan:
Ran these commands manually on jenkins, then ran 'date' and saw it
show the date in PDT.