Bugfix/esp8266 http client

[Jeroen88]

Removed unnecessary code

[Jeroen88]

@earlephilhower The current version of the library does not handle Connections that may be reused correctly. If the programmer calls end() directly, the connection may be reused, so it should NOT be _client->stop() nor should _client = nullptr and also not _tcpDprecated.reset(nullptr)!!!

If end() is called from begin() the connection should also not be closed, for the same reason. The only exception to this is when a changeover is made from the old api to the new or vice versa.

However, just before destruction ~ESP8266HTTPClient() the connection should be _client->stop(), because now the connection will be definitely closed. In the previous versions the destructor took care of this, but not anymore because of the bugfix.
I think it would be the best solution if it would still be possible to have the destructor stop the connection, but I do not know how. The only option I can think of is a new function that should be called before the ESP8266HTTPClient is destructed, but this changes the API and is error prone. Any ideas?