rdbms: make Database query error handling more strict

rdbms: make Database query error handling more strict

Handle all errors in query() that might have caused rollback by
putting the Database handle into an error state that can only be
resolved by cancelAtomic() or rollback(). Other queries will be
rejected until then.

This results in more immediate exceptions in some cases where
atomic section mismatch errors would have been thrown, such as a
an error bubbling up from a child atomic section. Most cases were
a try/catch block assumes that only the statement was rolled back
now result in an error and rollback.

Callers using try/catch to handle key conflicts should instead use
SELECT FOR UPDATE to find conflicts beforehand, or use IGNORE, or
the upsert()/replace() methods. The try/catch pattern is unsafe and
no longer allowed, except for some common errors known to just
rollback the statement. Even then, such statements can come from
child atomic sections, so committing would be unsafe. Luckily, in
such cases, there will be a mismatch detected on endAtomic() or a
dangling section detected in close(), resulting in rollback.

Remove caching from DatabaseMyslBase::getServerVariableSettings
in case some SET query changes the values.

Bug: T189999
Change-Id: I532bc5201681a915d0c8aa7a3b1c143b040b142e