In the FreeSWITCH core, the return value of switch_case_db_test_reactive
is ignored, but it is usable in LUA modules (and other bindings via
SWIG). The LUA API example[1] shows how to check the return value, but
that example miserably fails if the database did not exist before.

Changes:

 - Document the expected behavior of the test_reactive function.
 - Assert that test_sql and sql_reactive are both given. If either
   query is not given, the caller is using the wrong API.
 - When SCF_AUTO_SCHEMAS is cleared, use the return value of the
   test_sql execution. Does anybody use this? Why not remove it?
 - Do not unconditionally return SWITCH_FALSE when test_sql fails,
   instead allow it to become SWITCH_TRUE when reactive_sql passes.
 - Remove the unnecessary test_sql check for SCDB_TYPE_CORE_DB
   (this is now enforced through an assert check). (+reindent)
 - Clarify the error message of drop_sql, prepending "Ignoring" to
   the "SQL ERR" message.
 - LUA: Do not print "DBH NOT Connected" if the query fails. This was
   the initial source of confusion.

 [1]: https://confluence.freeswitch.org/display/FREESWITCH/Lua+API+Reference