first refactoring fr *.bats according to shellcheck

test/mail_with_relays.bats

@@ -12,10 +12,10 @@ function setup_file() {
     # We use a temporary config directory since we'll be dynamically editing
     # it with setup.sh.
     tmp_confdir=$(mktemp -d /tmp/docker-mailserver-config-relay-hosts-XXXXX)
-    cp -aT test/config/relay-hosts "$tmp_confdir"
+    cp -aT test/config/relay-hosts "${tmp_confdir}"
 
     docker run -d --name mail_with_relays \
-            -v "$tmp_confdir":/tmp/docker-mailserver \
+            -v "${tmp_confdir}":/tmp/docker-mailserver \
             -v "$(pwd)/test/test-files":/tmp/docker-mailserver-test:ro \
             -e RELAY_HOST=default.relay.com \
             -e RELAY_PORT=2525 \
@@ -24,17 +24,17 @@ function setup_file() {
             --cap-add=SYS_PTRACE \
             -e PERMIT_DOCKER=host \
             -e DMS_DEBUG=0 \
-            -h mail.my-domain.com -t ${NAME}
+            -h mail.my-domain.com -t "${NAME}"
         wait_for_finished_setup_in_container mail_with_relays
 }
 
 function teardown_file() {
     docker rm -f mail_with_relays
-    rm -rf "$tmp_confdir"
+    rm -rf "${tmp_confdir}"
 }
 
 @test "first" {
-  # this test must come first to reliably identify when to run setup_file
+  skip 'this test must come first to reliably identify when to run setup_file'
 }
 
 @test "checking relay hosts: default mapping is added from env vars" {
@@ -87,5 +87,5 @@ function teardown_file() {
 }
 
 @test "last" {
-  # this test is only there to reliably mark the end for the teardown_file
+  skip 'this test is only there to reliably mark the end for the teardown_file'
 }