obslog remains many `idle in transaction` in opDB

There remains many `idle in transaction` from 133.40.164.93, which leads the maximum connections of 200. Some of the reasons have been pinned down and some querying functionality in obslog has been temporarily disabled but happened again today. Please fix the root cause if possible.

Suggestions from Craig:

We should probably all use some client-side connection pooling, which is builtin to current psycopgs. And in any case make sure we are using context managers on the connections. Should be we be using server-side pooling, like with pgbouncer? I think best practice for actual concurrent connection limits to the db is based on cpus and disks, and that 200 is already too high.