tf-a-builder: Add parameter to control number of LAVA job retries

Per https://linaro.atlassian.net/browse/TFC-449

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: Iec9442db61f6dca3db80f9c8c7a78a74397842cb
diff --git a/tf-a-builder.yaml b/tf-a-builder.yaml
index 6bb0702..baeae33 100644
--- a/tf-a-builder.yaml
+++ b/tf-a-builder.yaml
@@ -85,6 +85,11 @@
             name: QA_TOOLS_BRANCH
             default: 'master'
         - string:
+            name: LAVA_RETRIES
+            default: 3
+            description: |
+              Number of tries submitting job to LAVA in case it fails (stopgap measure against nondeterministic failures)
+        - string:
             name: SHARE_FOLDER
             default: '/srv/shared/${JOB_NAME}/${BUILD_NUMBER}'
             description: 'Folder containing shared repositories for downstream pipeline jobs'
@@ -164,7 +169,7 @@
                                 # FVP jobs may hang at some particular TFTF test (see
                                 # https://linaro.atlassian.net/browse/TFC-176)
                                 passed=0
-                                for i in $(seq 1 3); do
+                                for i in $(seq 1 ${LAVA_RETRIES:-3}); do
                                     echo "# LAVA submission iteration #$i"
                                     if $submit_job; then
                                         passed=1