Fixes a recovery issue with deleted nodes

There was an issue where this scenario might happen:

 - TX1: Node N exists and has property record P
 - rotate log
 - TX2: P gets changed
 - TX3: N gets deleted (also P, but that's irrelevant for this scenario)
 - N is persisted to disk for some reason
 - crash
 - recover
 - TX2: P has changed and updates to indexes are gathered. As
   part of that it tries to read the labels of N (which does not
   exist a.t.m.)

We can actually just assume that if this happens and we're in
recovery mode that the node in question will be deleted in an
upcoming transaction, so just skip this update.