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 .
```

plugins/ps/subcommands/restore

@@ -1,5 +1,6 @@
 #!/usr/bin/env bash
-set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
 source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
 source "$PLUGIN_AVAILABLE_PATH/config/functions"
 source "$PLUGIN_AVAILABLE_PATH/ps/functions"
@@ -27,11 +28,11 @@ ps_restore_cmd() {
     ps_restore_all
   fi
 }
-  
+
 ps_restore_all() {
   local GNU_PARALLEL
 
-  if which parallel > /dev/null 2>&1; then
+  if which parallel >/dev/null 2>&1; then
     dokku_log_info1 "Restarting in parallel"
     GNU_PARALLEL=$(parallel -V 2>&1 | grep GNU || true)
     if [[ -z "$GNU_PARALLEL" ]]; then