List of regular expressions naming nodes to be excluded from cleaning.

Normally, a node property would be set on a node to indicate that it should be excluded from cleanup activities. e.g. dynamically-created nodes that are used once and then thrown away. However, not all node technologies support node properties, so in this case a set of regular expressions can be provided that will be matched against the node name and, if any regex matches a node name, that node will be excluded from cleanup activities.

Each (non-empty) line must be a valid regular expression. e.g. ^docker-.*$

Note: For the purposes of this matching, the name of the master node is the empty string not "master" so, if you want to exclude the master node from cleaning, you'll need to include a line saying ^$