Add a timeout to the wal_e cronjob

This puts a two hour timeout on the weekly basebackup with wal-e.

The timeout can be changed by adding setting a new tmeout_cmd in a data bag.

@vnivargi
Oh, I guess that got added after util-linux 2.20.1 (the version on osiris).

My workstation is running util-linux 2.24.2  
I will remove it.