control plugin serialization explicitly to avoid caching problem

test plan:
 * configure kaltura for an account
 * you should not get errors about dump_data on a Proc

Change-Id: I2c7b1ef104336d3d2f5b4f12302a5f25d1ce630e
Reviewed-on: https://gerrit.instructure.com/25218
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

Author: ccutrer

lib/canvas/plugin.rb

@@ -44,7 +44,17 @@ def initialize(id, tag=nil)
               :base=>nil
       }.with_indifferent_access
     end
-    
+
+
+    # custom serialization, since the meta can containt procs
+    def _dump(depth)
+      self.id.to_s
+    end
+
+    def self._load(str)
+      find(str)
+    end
+
     def default_settings
       settings = @meta[:settings]
       settings = settings.call if settings.respond_to?(:call)