tests/qtest: add TIMEOUT_MULTIPLIER

Some tests need more time when qemu is built with
"--enable-asan --enable-ubsan"

As was discussed here:
https://patchew.org/QEMU/20241112120100.176492-2-frolov@swemel.ru/

TIMEOUT_MULTIPLIER enviroment variable will be
a useful option, allowing non-invasive timeouts
increasing for a specific build.

Signed-off-by: Dmitry Frolov <frolov@swemel.ru>
Tested-by: Fabiano Rosas <farosas@suse.de>
[changed from ifndef to ?=]
Signed-off-by: Fabiano Rosas <farosas@suse.de>
1 file changed