tf-a-builder: switch license server

On the speculation that the random license issues are due to
jenkins server overloading from license requests, try using
another server for flexnet.

Change-Id: Ibc78aa040a2675fa5563938f61142c20d5e93f5f
diff --git a/tf-a-builder.yaml b/tf-a-builder.yaml
index 3389194..17ac742 100644
--- a/tf-a-builder.yaml
+++ b/tf-a-builder.yaml
@@ -108,7 +108,7 @@
             default: '987685672616.dkr.ecr.us-east-1.amazonaws.com'
         - string:
             name: ARMLMD_LICENSE_FILE
-            default: '27000@ci.trustedfirmware.org'
+            default: '27000@flexnet.trustedfirmware.org'
         - string:
             name: JUNO_ROOTFS_URL
             default: 'http://releases.linaro.org/openembedded/aarch64/17.01/linaro-image-minimal-genericarmv8-20170127-888.rootfs.tar.gz'