fix 1386: enhance on lock procedure

locking of ro_tasks for HA enhancements:
- lock time is configurable by ro.cfg or ENV
(OSMRO_SERVER_TASK_LOCKED_TIME)
- lock time is reduced to 10min by default
- lock is renewed when needed by a new asyncio task at vim_admin

Change-Id: Icae02803e57713aca2f028884142fa152ee3d032
Signed-off-by: tierno <alfonso.tiernosepulveda@telefonica.com>