selinux-testsuite: consolidate network timeouts
    
    There are several places in the testuite that set timeouts for network
    operations. They use different values in different places and
    particularly for the SCTP test the value is too small on some machines
    and often leads to false-positive test failures.
    
    Since the right value depends on the environment, rather than proposing
    to change the value to some guessed number upstream, let's just tweak
    the number from the wrapper and suggest updating the numbers upstream
    once we find a "proven" good value.
    
    I'm setting the default to 4 secs - 1 second higher than the old value
    in the inet_socket test, where we also (very) sporadically get failures.
    The most problematic SCTP subtest had 2 seconds timeout before.
    
    Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>