[failure-diagnosis enhancement]awe-server API can provide more info for workunit failure.

new API:

* view awe-client error log related to the failed workunit (need client side config: [Client] print_app_msg=True):

<code>curl -X GET http://\<awe_api_url\>/work/\<work_id\>?report=worknotes</code>

existing similar API

* view stdout of one workunit (need client side config: [Client] print_app_msg=True)

<code>curl -X GET http://\<awe_api_url\>/work/\<work_id\>?report=stdout</code>

* view stderr of one workunit (need client side config: [Client] print_app_msg=True)

<code>curl -X GET http://\<awe_api_url\>/work/\<work_id\>?report=stderr</code>