Removing TS Gateway breaking BIO_clear_flags() call

The current master/HEAD does not work correctly with terminal server gateways when a particular BIO_clear_flags() function is called.

According to @Ofloo in #2056: 
> The issue appeared between 01c557d .. 3fce288 "Fix unclean SSL disconnection"
> 01c557d works fine
> 3fce288 gives me this error and doesn't even show a window just that error

I tried reverting the commit. Git couldn't auto merge, so decided to debug the few changed lines. I've narrowed the problem down to a single function call. This pull request simply removes the function call causing the problem. I'm not sure this is the ideal fix for this issue, but the removal of this single function call gives me a working FreeRDP installation. I'm hoping one of the project maintainers can say "OMG that's perfect/wrong!" and we can get this corrected.

An example of my command line and the failing results:
```
$ xfreerdp /g:tsg.mywork.com /v:rdp.mywork.com /u:username /p:password /d:mywork /w:1280 /h:1024 /cert-ignore
[00:17:40:522] [18375:18376] [INFO][com.freerdp.core.gateway.tsg] - TS Gateway Connection Success
[00:17:40:664] [18375:18376] [ERROR][com.freerdp.core] - freerdp_set_last_error 0x2000D
$
```
I don't know which version of Windows Terminal Server I'm connecting to, but can find out if that's relevant.

Thanks!