server-mux: Keep listening after Accept() err (#3613)
server-mux: Keep listening after Accept() err (#3613)

Accept() can return errors like: `too many open files`, no need to totally quit listening in this case.
aead/minio,vadmeste/minio,brendanashworth/minio,dvstate/minio,vadmeste/minio,luomeiqin/minio,fwessels/minio,luomeiqin/minio,donatello/minio,abperiasamy/minio,harshavardhana/minio,rushenn/minio,aead/minio,dvstate/minio,balamurugana/minio,harshavardhana/minio,brendanashworth/minio,luomeiqin/minio,harshavardhana/minio,abperiasamy/minio,harshavardhana/minio,krisis/minio,krishnasrinivas/minio,abperiasamy/minio,balamurugana/minio,aead/minio,jimjag/minio,aead/minio,minio/minio,brendanashworth/minio,jimjag/minio,dvstate/minio,minio/minio,fwessels/minio,krishnasrinivas/minio,NitishT/minio,hackintoshrao/minio,krisis/minio,NitishT/minio,rushenn/minio,hackintoshrao/minio,aead/minio,donatello/minio,jimjag/minio,harshavardhana/minio,abperiasamy/minio,rushenn/minio,dvstate/minio,hackintoshrao/minio,fwessels/minio,aead/minio,NitishT/minio,aead/minio,harshavardhana/minio,harshavardhana/minio,dutchcoders/minio,dutchcoders/minio,krishnasrinivas/minio,dutchcoders/minio,krishnasrinivas/minio,aead/minio,NitishT/minio,fwessels/minio,harshavardhana/minio,luomeiqin/minio,rushenn/minio,brendanashworth/minio,dutchcoders/minio,hackintoshrao/minio,jimjag/minio