Looking at GP documents, there is no indication that master dbid
must be 1. However, when CREATE_QD_DB, gpinitsystem always writes
"gp_dbid=1" into file `internal.auto.conf` even if we specify:

```
mdw~5432~/data/master/gpseg-1~2~-1
 OR
mdw~5432~/data/master/gpseg-1~0~-1
```

But catalog gp_segment_configuration can have the correct master
dbid value (2 or 0), the mismatch causes gpinitsystem hang.
Users can run into such problem for their first time to use
gpinitsystem -I.

Here we test dbid 0, because PostmasterMain() will simply check
dbid >= 0 (non-utility mode), it says:

> This value must be >= 0, or >= -1 in utility mode

It seems 0 is a valid value.

Changes:

- use specified master dbid field when CREATE_QD_DB.
- remove unused macros MASTER_DBID, InvalidDbid in C sources.
Reviewed-by: NAshwin Agrawal <aashwin@vmware.com>