Detect and exit when persistent storage can't mmap a file at the required address.

Change-Id: If7e9218b815a53160b4be197e155df1912fe20ac
varnish (3.0.3plus~rc1-wm13) precise; urgency=low

  * Detect and exit when persistent storage can't mmap a file at the
  * required address

Change-Id: Ie1238dc1789b071dd1d81c36572893e2cc10aec1