tests: Support --config to enable tests to override config defaults

tests: Support --config to enable tests to override config defaults

Implements a simple mechanism to allow tests to customize the
configuration.  For a given <name>-test.c just place a <name>.ini file
at the same location as the test itself.  Alternately, you can generate
a <name>.ini in the same directory that the compiled test is placed
(i.e. the top builddir).  If no configuration file is found, then no
configuration will be used (i.e. --no-config is specified.)

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-By: Derek Foreman <derekf@osg.samsung.com>