cleanup deb pre-existing builds

Change-Id: Ic91ef2d5fd65b3a45e449c84afe9d5877d065720
Signed-off-by: Mike Marchetti <mmarchetti@sandvine.com>
diff --git a/jenkins/osmclient/start_build b/jenkins/osmclient/start_build
index df4fc27..2206a1a 100755
--- a/jenkins/osmclient/start_build
+++ b/jenkins/osmclient/start_build
@@ -37,6 +37,10 @@
 apt update
 apt install -y docker.io
 
+# cleanup all pre-existing builds.
+# deb pkg build fails if previous build image is present
+rm -rf deb_dist dist
+
 docker build -t $OSM_MDG .
 DOCKER_ARGS="-v $(pwd):$(pwd) -w $(pwd) -u $(id -u):$(id -g) $OSM_MDG"