Bug #751 don't exit after send error

[fklassen]

Sample output:

/Users/fklassen/git/tcpreplay/build/src/tcpreplay -i en0 -t pkt_too_long.pcap
Actual: 2 packets (196 bytes) sent in 0.000066 seconds
Rated: 2969696.9 Bps, 23.75 Mbps, 30303.03 pps
Flows: 2 flows, 30303.03 fps, 3 flow packets, 0 non-flow
Statistics for network device: en0
    Successful packets:        2
    Failed packets:            1
    Truncated packets:         0
    Retried packets (ENOBUFS): 0
    Retried packets (EAGAIN):  0
Warning in /Users/fklassen/git/tcpreplay/src/send_packets.c:send_packets() line 489:
Unable to send packet: Error with bpf send() [2]: Input/output error (errno = 5)

Process finished with exit code 0