tf-a-builder: Set LAVA_RETRIES to 2

The idea was to pass this setting from top-level jobs, but that doesn't
work for e.g. the l2 job. So, instead just set more conservative default.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I1e8dae69fcffb3e16ce3a10c2faba81361944793
1 file changed