Reset environment of the jailed process

According to `jexec(1)`:

>   -l      Execute in a clean environment.  The environment is
>           discarded except for HOME, SHELL, TERM, USER, and anything
>           from the login class capability database for the user.

Author: smortex

lib/bolt/transport/jail/connection.rb

@@ -49,7 +49,7 @@ def connect
         end
 
         def execute(command)
-          args = ["-U", @user]
+          args = ['-lU', @user]
 
           jail_command = %w[jexec] + args + [jail_id] + Shellwords.split(command)
           @logger.trace { "Executing #{jail_command.join(' ')}" }