Bring it out of sysdb, which will slowly remove internal dependencies on
domains and instead will always require them to be passed by callers.

Removing bad examples of usage of sysdb_transaction_start/commit/end
functions and making it more consistent (all files except of
src/db/sysdb_*.c).

The compilation produced an error due to missing declaration of uint32_t
and a couple of warnings caused by different prototypes of argument
parsing functions in older Python releases.

The error handler would simply fall through instead of returning NULL.

This is mostly a cosmetic patch.

The purpose of wrapping a multi-line macro in a do { } while(0) is to
make the macro usable as a regular statement, not a compound statement.

When the while(0) is terminated with a semicolon, the do { } while(0);
block becomes a compound statement again.

The patch also updates code using modified functions. Tests have also
been adjusted.