glib-2.0: disable tests for native builds, and respect ptest for LSB

glib-2.0: disable tests for native builds, and respect ptest for LSB

Without disabling the tests in the native build, glib-2.0-native will need
libdbus-native to be present.  As we don't run the tests, disable them so we
don't have build failures due to missing dependencies.

Also, the LSB override was missing PTEST_CONF so the same problem could happen.
After adding PTEST_CONF the LSB override is identical to the non-overridden
EXTRA_OECONF, so remove it.

Finally, to be explicit, put --enable-module-tests in PTEST_CONF.

(From OE-Core rev: 395b90054eccddc1c9062a9a8657ed4482b7710a)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>