Attempting to be more robust against problems initializing this class.

https://jenkins.ci.cloudbees.com/job/core/job/jenkins_main_trunk/896/testReport/junit/hudson.tools/ToolLocationNodePropertyTest/testFormRoundTrip/
java.lang.NoClassDefFoundError: Could not initialize class hudson.model.ComputerSet
	at jenkins.model.Jenkins.getComputer(Jenkins.java:1107)

core/src/main/java/hudson/model/ComputerSet.java

@@ -426,8 +426,8 @@ public final class ComputerSet extends AbstractModelObject implements Describabl
                         r.add(i);
                 }
             monitors.replaceBy(r.toList());
-        } catch (IOException e) {
-            LOGGER.log(Level.WARNING, "Failed to instanciate NodeMonitors",e);
+        } catch (Throwable x) {
+            LOGGER.log(Level.WARNING, "Failed to instantiate NodeMonitors", x);
         }
     }