Merge "Capture the log in default"

.testr.conf

 [DEFAULT]
 test_command=OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
              OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
+             OS_LOG_CAPTURE=${OS_LOG_CAPTURE:-1} \
              OS_TEST_TIMEOUT=${OS_TEST_TIMEOUT:-7200} \
              ${PYTHON:-python} -m subunit.run discover ${OS_TEST_PATH:-./tests} $LISTOPT $IDOPTION
 test_id_option=--load-list $IDFILE