Current version of qperf throws errors in environment with only ipv4 address

[SangameshwarBabu]

    With ipv6.disable in kernel command line ipv6 protocol is disabled and qperf throws below error in such environments :

    # qperf
    unable to bind to listen port

    strace :
9052  14:24:36.118470 socket(AF_INET6, SOCK_STREAM, IPPROTO_TCP) = -1 EAFNOSUPPORT (Address family not supported by protocol) <0.001313>
9052  14:24:36.119820 fstat(1</dev/pts/0<char 136:0>>, {st_dev=makedev(0, 23), st_ino=3, st_mode=S_IFCHR|0620, st_nlink=1, st_uid=0, st_gid=5, st_blksize=1024, st_blocks=0, st_rdev=makedev(136, 0), st_atime=1651602272 /* 2022-05-03T14:24:32.680622196-0400 */, st_atime_nsec=680622196, st_mtime=1651602272 /* 2022-05-03T14:24:32.680622196-0400 */, st_mtime_nsec=680622196, st_ctime=1651602034 /* 2022-05-03T14:20:34.680622196-0400 */, st_ctime_nsec=680622196}) = 0 <0.000005>
9052  14:24:36.119866 write(1</dev/pts/0<char 136:0>>, "unable to bind to listen port\n", 30) = 30 <0.000039>
9052  14:24:36.119950 exit_group(1)     = ?
9052  14:24:36.120060 +++ exited with 1 ++

    With qperf version 0.4.9 we defined AI_FAMILY as AF_UNSPEC, starting
    qperf 0.4.11 the same is changed to AF_INET6 which causes issues
    when ipv6 is disabled at protocol layer (as a kernel command line
    arguement). This patch reverses the behavior.