Fix #914: catch EtcdKeyNotFound as well as EtcdCompareFailed.
Fix #914: catch EtcdKeyNotFound as well as EtcdCompareFailed.

neiljerram/felix,matthewdupre/felix,TrimBiggs/calico,neiljerram/felix,TrimBiggs/calico,Metaswitch/calico,alexhersh/calico,matthewdupre/felix,neiljerram/felix,alexhersh/calico,neiljerram/felix,Metaswitch/calico