Made lease id optional in create_lease logging

Fixed a crash that happened when a user tried to create a lease with a
before_end_lease date sooner than the start_date date.
When this situation happened a log line crashed because it was trying
to access the lease id, which was not defined at that moment.

Change-Id: I846761eb447d18892d0ad8910df22784d73b2bf9
Closes-Bug: #1326523
Merge "Made lease id optional in create_lease logging"