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/plugin/subcommands/default

@@ -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/plugin/internal-functions"
 

plugins/plugin/subcommands/disable

@@ -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 "$PLUGIN_AVAILABLE_PATH/plugin/functions"
 source "$PLUGIN_AVAILABLE_PATH/plugin/internal-functions"

plugins/plugin/subcommands/enable

@@ -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 "$PLUGIN_AVAILABLE_PATH/plugin/functions"
 source "$PLUGIN_AVAILABLE_PATH/plugin/internal-functions"

plugins/plugin/subcommands/install

@@ -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 "$PLUGIN_AVAILABLE_PATH/plugin/functions"
 source "$PLUGIN_AVAILABLE_PATH/plugin/internal-functions"
@@ -12,7 +13,7 @@ plugin_install_cmd() {
       [[ "$#" -gt 2 ]] && dokku_log_info1_quiet "Cannot install additional core plugins, running core plugin install trigger"
       PLUGIN_PATH="$PLUGIN_CORE_PATH" plugn trigger install
       ;;
-    https:*|git*|ssh:*|*.tar.gz|*.tgz)
+    https:* | git* | ssh:* | *.tar.gz | *.tgz)
       shift
       download_and_enable_plugin "$@"
       plugn trigger install

plugins/plugin/subcommands/install-dependencies

@@ -1,5 +1,6 @@
 #!/usr/bin/env bash
-set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
 
 plugin_install_dependencies_cmd() {
   declare desc="calls dependencies plugin trigger via command line"

plugins/plugin/subcommands/list

@@ -1,5 +1,6 @@
 #!/usr/bin/env bash
-set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
 source "$PLUGIN_AVAILABLE_PATH/plugin/internal-functions"
 
 plugin_list_cmd "$@"

plugins/plugin/subcommands/uninstall

@@ -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 "$PLUGIN_AVAILABLE_PATH/plugin/functions"
 source "$PLUGIN_AVAILABLE_PATH/plugin/internal-functions"

plugins/plugin/subcommands/update

@@ -1,5 +1,6 @@
 #!/usr/bin/env bash
-set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
 source "$PLUGIN_AVAILABLE_PATH/plugin/internal-functions"
 
 plugin_update_cmd() {