webui: add cleanup method for dynamic logging
webui: add cleanup method for dynamic logging

Former-commit-id: 40b6232848bcd160ff669a9c5b221f8057a6c107 [formerly 9df62582a6956a77e89a821d8ff88a92ee80e07d]
Former-commit-id: bef369fdcd7754ef813da34dcba8065f860bbeab
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine