connect: support to pass addrs in a file as an argument

[yuuki]

ubuntu@shawk-client-01:~$ cat ./file_addrs
10.0.150.2:9100 10.0.150.2:9101

ubuntu@shawk-client-01:~$ ./connperf connect --proto tcp --flavor ephemeral --rate 1000 --duration 1200s --addrs-file ./file_addrs
PEER                 CNT        LAT_MAX(µs)     LAT_MIN(µs)     LAT_MEAN(µs)    LAT_90p(µs)     LAT_95p(µs)     LAT_99p(µs)     RATE(/s)
10.0.150.2:9100      5000       206664          181             711             412             442             529             1000.07
10.0.150.2:9101      4998       211987          208             991             456             494             739             999.70