gitignore: add ".Dockerfile-functional-tester"

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

.gitignore

@@ -7,7 +7,6 @@
 /release
 /machine*
 /bin
-.Dockerfile-test
 .vagrant
 *.etcd
 *.log
@@ -15,8 +14,6 @@
 *.swp
 /hack/insta-discovery/.env
 *.test
-tools/functional-tester/docker/bin
-hack/scripts-dev/docker-dns/.Dockerfile
-hack/scripts-dev/docker-dns-srv/.Dockerfile
 hack/tls-setup/certs
 .idea
+*.bak