Fix race condition in RedisCacheTest.ShutDownDuringConnection
Fix race condition in RedisCacheTest.ShutDownDuringConnection

It was not waiting until RedisNotRespondingServerThread actually receives connection, which resulted in TcpServerThreadForTesting failure. Other tests do not need to explicitly wait on that because they rely on what server thread answers to the client.

pagespeed/mod_pagespeed,VersoBit/mod_pagespeed,hashashin/src,VersoBit/mod_pagespeed,hashashin/src,VersoBit/mod_pagespeed,pagespeed/mod_pagespeed,pagespeed/mod_pagespeed,hashashin/src,hashashin/src,hashashin/src,VersoBit/mod_pagespeed,hashashin/src,VersoBit/mod_pagespeed,VersoBit/mod_pagespeed,pagespeed/mod_pagespeed,pagespeed/mod_pagespeed,hashashin/src,pagespeed/mod_pagespeed,pagespeed/mod_pagespeed,hashashin/src,VersoBit/mod_pagespeed