Handle an exception from target.perf_capture_queue

Prevent a single target.perf_capture_queue exception from preventing the
rest of the targets from being queued.  If an invalid target made its
way into the targets list and perf_capture_queue throws an exception
then currently the remaining list of targets won't be queued.

https://bugzilla.redhat.com/show_bug.cgi?id=1439888

app/models/metric/capture.rb

@@ -213,9 +213,13 @@ def self.queue_captures(targets, target_options)
 
       options = target_options[target]
 
-      target.perf_capture_queue(interval_name, options)
-      if !target.kind_of?(Storage) && use_historical && target.last_perf_capture_on.nil?
-        target.perf_capture_queue('historical')
+      begin
+        target.perf_capture_queue(interval_name, options)
+        if !target.kind_of?(Storage) && use_historical && target.last_perf_capture_on.nil?
+          target.perf_capture_queue('historical')
+        end
+      rescue => err
+        _log.warn("Failed to queue perf_capture for target [#{target.class.name}], [#{target.id}], [#{target.name}]: #{err}")
       end
     end
   end