webui: replace redundant code with utils.getusername()
webui: replace redundant code with utils.getusername()

Former-commit-id: 16668bd6c996fb9b23c9cf03adacb9df6d98324c [formerly 16668bd6c996fb9b23c9cf03adacb9df6d98324c [formerly 38caef69c50d2a92d8a64230fe0f4c9dcc6a5c9c]]
Former-commit-id: 3dcecfff5157698c9562d6ef40def7987268e5dd
Former-commit-id: 6be1e7e9859a5843f688fe876db3acf49feb225e
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine