loadResource(Path) in Configuration.java is assuming that only paths that can come to this method can be on local file system. But jobconf_history.jsp sends Path that is there on DFS causing this NPE. As it is assuming the path to be local file system, looks like fixing Configuration.java seems to be not possible.
Regarding getting job view ACLs from history file: As getting job view ACLs from conf file is also going to DFS twice(once for loading the JobConf, and one more time for passing it to the xml formatter), getting job view ACLs from history file also seems reasonable. Also, since jobconf_history.jsp is the only JSP that is currently getting ACLs from conf file and every other history related JSP is getting the ACLs from history file itself, making this change would make things consistent also.