[test] give a non-ambiguous order to sync_schema assertion (closes #3001959)
Sorting by ordernum alone is unstable since several values have the
same ordernum.
ordernum + name should be stable.
[schema,server] add a security debugging aid (closes #2920304)
- Add a DGB_SEC debugging flag (to be used with set_debug/debugged).
- Add a context manager (tunesecurity) to filter security assertions.
Note: this does not address all read-security mecanisms.