formatted awless completion and used helper function

clean_files.txt

@@ -57,6 +57,7 @@ plugins/available/xterm.plugin.bash
 
 # completions
 #
+completion/available/awless.completion.bash
 completion/available/brew.completion.bash
 completion/available/cargo.completion.bash
 completion/available/knife.completion.bash

completion/available/awless.completion.bash

@@ -1 +1,5 @@
-[[ -x "$(which awless)" ]] && source <(awless completion bash)
+# shellcheck shell=bash
+if _command_exists awless; then
+	# shellcheck disable=SC1090
+	source <(awless completion bash)
+fi