need to resurrect function to write-protect ODB unless we are writing to ODB.

[dd1]

need to resurrect function to write-protect ODB unless we are writing to ODB. Functions that only read from ODB should not turn off write-protect. I think the code for this exists, but was not used recently. K.O.

[dd1]

Initial support in commit fe36aa4. Enabled by "/experiment/protect odb". K.O.

[dd1]

almost usable on the branch midas-2017-10, except that cm_watchdog() cannot update odb last_activity() because of no write access to odb... K.O.

[dd1]

cm_watchdog() works now. testing in the agdaq now. K.O.

[dd1]

testing in agdaq system completed, works now. branch midas-2017-10. K.O.