def user_chpasswd(user_id, password)
      payload = {
        :password => password, 
        :json => 1
      }
      res = http_put(:uri=>"/users/#{user_id}/chpasswd", :data=>payload, :fields=>x_cookie)
      return res.code
    end
def user_chpasswd(user_id, password)
      payload = {
        :password => password, 
        :json => 1
      }
      res = http_put(:uri=>"/users/#{user_id}/chpasswd", :data=>payload, :fields=>x_cookie)
      return res.code
    end
change password for user_id

 returns: result code

 Usage:

  n=NessusREST::Client.new (:url=>'https://localhost:8834', :username=>'user', :password=> 'password')
  puts n.user_chpasswd(1,'newPassword')