tool_context: correct default for bashcompletion

Signed-off-by: Jean Privat <jean@pryen.org>
tool_context: just print the bash_completion, let the caller do what it want

Signed-off-by: Jean Privat <jean@pryen.org>
tool_context: do not need an attribute bash_completion

Signed-off-by: Jean Privat <jean@pryen.org>
tests: update test_toolcontext

Signed-off-by: Jean Privat <jean@pryen.org>
bash_completion: add a magic script that do the bash_completion setup

Signed-off-by: Jean Privat <jean@pryen.org>