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/logs/subcommands/failed

@@ -2,11 +2,13 @@
 source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
 source "$PLUGIN_AVAILABLE_PATH/apps/functions"
 source "$PLUGIN_AVAILABLE_PATH/config/functions"
-set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
 
 cmd-logs-failed() {
   declare desc="shows the last failed deploy logs"
-  declare cmd="logs:failed" argv=("$@"); [[ ${argv[0]} == "$cmd" ]] && shift 1
+  declare cmd="logs:failed" argv=("$@")
+  [[ ${argv[0]} == "$cmd" ]] && shift 1
   declare APP="$1"
   local DOKKU_SCHEDULER