Reduce how often CI builds download Gradle

Closes gh-40

ci/images/setup.sh

@@ -58,5 +58,3 @@ mkdir -p /opt/gradle
 cd /opt/gradle
 curl -L $GRADLE_URL | bsdtar --strip-components=1 -xvf-
 chmod +x /opt/gradle/bin/gradle
-mkdir ~/.gradle
-echo 'systemProp.user.name=concourse' > ~/.gradle/gradle.properties

ci/scripts/common.sh

@@ -1,3 +1,5 @@
 source /opt/concourse-java.sh
 
 setup_symlinks
+
+echo 'systemProp.user.name=concourse' > ~/.gradle/gradle.properties

ci/scripts/smoke-test.sh

@@ -4,5 +4,5 @@ set -e
 source $(dirname $0)/common.sh
 
 pushd git-repo > /dev/null
-./gradlew --no-daemon ${SMOKE_TEST}:${TASK}
+gradle --no-daemon ${SMOKE_TEST}:${TASK}
 popd > /dev/null