socket: persist connect and listen errors

[daurnimator]

Linux has been seen to not repeat errors certain UDP errors:

socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 5
open("/dev/urandom", O_RDONLY|O_NOCTTY|O_NONBLOCK) = 6
fstat(6, {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 9), ...}) = 0
poll([{fd=6, events=POLLIN}], 1, 10)    = 1 ([{fd=6, revents=POLLIN}])
read(6, "#\361x\3\34\34\302\251\243\"\361\304\0\346\372eh [5K\303\347\27\334\371pY\376\231\2431", 32) = 32
close(6)                                = 0
getuid()                                = 1000
bind(5, {sa_family=AF_INET, sin_port=htons(12738), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
connect(5, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 16) = 0
sendto(5, "\320O\1\0\0\1\0\0\0\0\0\0\5wrong\7invalid\0\0\1\0\1", 31, 0, NULL, 0) = 31
recvfrom(5, 0x13353ec, 768, 0, NULL, NULL) = -1 ECONNREFUSED (Connection refused)
recvfrom(5, 0x13353ec, 768, 0, NULL, NULL) = -1 EAGAIN (Resource temporarily unavailable)

@wahern I noticed this today. no idea if my fix is along the correct lines.

Up to the first recvfrom is happening during dns resolution inside of cqueues.socket.connect.
The 2nd recvfrom is a following mysocket:connect() (which after getting EAGAIN hangs waiting for a reply which never comes.)

[daurnimator]

Possibly related to #156