fix building fresh docker images for integration tests

i always get bitten by some caching or missing checks when i use docker...
Dockerfile.moxmail doesn't exist anymore, but that doesn't matter, it doesn't
even look at it but will just use some image that is still around (based on the
name?) i suppose that means docker-compose also doesn't rebuild an image when
the dockerfile mentioned in the build changes.

Makefile

@@ -49,8 +49,8 @@ fuzz:
 
 
 test-integration:
-	docker image build --pull -f Dockerfile -t mox_integration_moxmail .
-	docker image build --pull -f testdata/integration/Dockerfile.test -t mox_integration_test testdata/integration
+	docker image build --pull --no-cache -f Dockerfile -t mox_integration_moxmail .
+	docker image build --pull --no-cache -f testdata/integration/Dockerfile.test -t mox_integration_test testdata/integration
 	-rm -rf testdata/integration/moxacmepebble/data
 	-rm -rf testdata/integration/moxmail2/data
 	-rm -f testdata/integration/tmp-pebble-ca.pem

docker-compose-integration.yml

@@ -1,6 +1,6 @@
 version: '3.7'
 services:
-  # We run integration_test.go from this container, it connects to both mox instances.
+  # We run integration_test.go from this container, it connects to the other mox instances.
   test:
     hostname: test.mox1.example
     image: mox_integration_test
@@ -86,10 +86,8 @@ services:
   localserve:
     hostname: localserve.mox1.example
     domainname: mox1.example
-    build:
-      dockerfile: Dockerfile.moxmail
-      context: testdata/integration
-    command: ["sh", "-c", "set -e; chmod o+r /etc/resolv.conf; go run . -- localserve -ip 172.28.1.60"]
+    image: mox_integration_moxmail
+    command: ["sh", "-c", "set -e; chmod o+r /etc/resolv.conf; mox localserve -ip 172.28.1.60"]
     volumes:
       - ./.go:/.go
       - ./testdata/integration/resolv.conf:/etc/resolv.conf