[BUG] srt-live-transmit removes a socket from epoll twice on connection timeout

[maxsharabayko]

Extracted from #1566
The issue can be simply reproduced, just trying to connect to some non-existing destination like this:

./srt-live-transmit "udp://:4201?a" srt://192.168.1.237:4200
Media path: 'udp://:4201?a' --> 'srt://192.168.1.237:4200'
13:27:29.628714/T0x106da3dc0*E:SRT.ea: IPE: remove_usock: @287539723 not found as either socket or group. 
Removing only from epoll system.

The IPE message comes from SRT, as srt-live-transmit tries to remove the same socket from epoll twice.

TODO:

• It is an error when an application tries to delete a socket that does not exist in epoll. But is it an IPE type error?
• Fix srt-live-transmit