task: default populate internal error

If a timeout happens, set internal error as default
message.

Tested: passes validator with valid message,
set very short timeout on long task to verify

Change-Id: I31e979df486f325d18ca2b0a94d585d38097b8e5
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/redfish-core/lib/task.hpp b/redfish-core/lib/task.hpp
index 4540c81..12425c1 100644
--- a/redfish-core/lib/task.hpp
+++ b/redfish-core/lib/task.hpp
@@ -158,6 +158,7 @@
                 self->finishTask();
                 self->state = "Cancelled";
                 self->status = "Warning";
+                self->messages.emplace_back(messages::internalError());
                 self->callback(ec, msg, self);
             });
     }