Section names "dbi-{hpss,crawler}"; dbtypes "{hpss,crawler}"

 - Provide variables with section names in CrawlDBI.py
 - Break make_tcfg() into separate routines for each db engine
 - Moved test_ctor_dbn_none() from DBI_in_Base to DBI_out_Base because it no
   long applies to db2 -- option 'dbname' is no longer required in the
   dbi-hpss section of the config file

Change-Id: If80e7407bafdd6a11c4a6d5c0eef4f7fb91fb3e4
WSREP retry, eliminate hard-coding

 - Make mysql select retry on WSREP failure
 - Soften references

Change-Id: I3472fc9ffb402141137b2d877904bb4e2a26521b