fix(tf-l2 job): fix gerrit variable names

TF-L jobs should set TF_GERRIT variables so these can be passed
correctly into tf-a-builder job, otherwise the latter test the default
parameter.

Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
Change-Id: I1b801bd71ec7835bd50ffc4e593eba756f8bbea5
1 file changed