Test Bonding.CloseGroupAndSocket tends to hang up in AppVeyor

[maxsharabayko]

AppVeyor Image: Visual Studio 2015; Configuration: Release; Platform: x64.
The latest master.

22: [ RUN      ] Bonding.CloseGroupAndSocket
22: Created group socket: 1863866117
22: Connecting two sockets 
22: Socket created: 790124292
22: Listen: wait for acceptability
22: Socket created: 790124290
22: Returned from connecting two sockets 
22: Listen: reported 1 acceptable and 0 errors
22: Listener will read packets...
22: Epoll result: 2
22: Epoll rlen: 0, wlen: 2
22: Epoll write[0]: 790124292 (removed from epoll)
22: Epoll write[1]: 1863866117 (removed from epoll)
22: Connect callback. Socket: 790124290, error: 1001, token: 2
22: 13:18:35.492000/T2772*E:SRT.ea: EID:3 no sockets to check, this would deadlock

[maxsharabayko]

Likely fixed by #2538.

[maxsharabayko]

Still observed sometimes with SRT v1.5.2-rc.1.
AppVeyor VS 2015 Release x86

231: [ RUN      ] Bonding.CloseGroupAndSocket
231: Created group socket: 1369380345
231: Connecting two sockets 
231: Socket created: 295638520
231: Listen: wait for acceptability
231: Socket created: 295638518
231: Returned from connecting two sockets 
231: Listen: reported 1 acceptable and 0 errors
231: Listener will read packets...
231: Epoll result: 2
231: Epoll rlen: 0, wlen: 2
231: Epoll write[0]: 295638520 (removed from epoll)
231: Epoll write[1]: 1369380345 (removed from epoll)
231: Connect callback. Socket: 295638518, error: 1001, token: 2
231: 17:30:01.425000/T2848*E:SRT.ea: EID:3 no sockets to check, this would deadlock