tests: run mvdan/shfmt on test runs

While I do not agree with _every_ style change, this will force Dokku to have consistent formatting across all shell scripts, which is arguably a Good Thing™.

The command used to reprocess everything is:

```shell
shfmt -l -bn -ci -i 2 -w .
```

tests/ci/setup.sh

@@ -45,12 +45,12 @@ install_dokku() {
 
   "${ROOT_DIR}/contrib/release" build
 
-  echo "dokku dokku/hostname string dokku.me"              | sudo debconf-set-selections
+  echo "dokku dokku/hostname string dokku.me" | sudo debconf-set-selections
   echo "dokku dokku/key_file string /root/.ssh/id_rsa.pub" | sudo debconf-set-selections
-  echo "dokku dokku/nginx_enable boolean true"             | sudo debconf-set-selections
-  echo "dokku dokku/skip_key_file boolean true"            | sudo debconf-set-selections
-  echo "dokku dokku/vhost_enable boolean true"             | sudo debconf-set-selections
-  echo "dokku dokku/web_config boolean false"              | sudo debconf-set-selections
+  echo "dokku dokku/nginx_enable boolean true" | sudo debconf-set-selections
+  echo "dokku dokku/skip_key_file boolean true" | sudo debconf-set-selections
+  echo "dokku dokku/vhost_enable boolean true" | sudo debconf-set-selections
+  echo "dokku dokku/web_config boolean false" | sudo debconf-set-selections
   sudo dpkg -i "$(cat "${ROOT_DIR}/build/deb-filename")"
 }
 

tests/ci/unit_test_runner.sh

@@ -1,7 +1,8 @@
 #!/usr/bin/env bash
 
 is_number() {
-  local NUMBER=$1; local NUM_RE='^[1-4]+$'
+  local NUMBER=$1
+  local NUM_RE='^[1-4]+$'
   if [[ $NUMBER =~ $NUM_RE ]]; then
     return 0
   else
@@ -33,6 +34,6 @@ for test in $TESTS; do
   fi
 
   endtest=$(date +%s)
-  testruntime=$((endtest-starttest))
+  testruntime=$((endtest - starttest))
   echo "individual runtime: $(date -u -d @${testruntime} +"%T")"
 done