util: Don't log errno on bad server address

From man inet_pton(3):

    inet_pton() returns 1 on success (network address was successfully
    converted). 0 is returned if src does not contain a character
    string representing a valid network address in the specified
    address family. If af does not contain a valid address family,
    -1 is returned and errno is set to EAFNOSUPPORT.

We can assume that the return value is 1 or 0 (because af is set to
AF_INET4 or AF_INET6), therefore errno will not be set.

If a user attempts to bind a server using invalid network address the
following error message will be shown:

 Bad server address: Success

Which is not very clear, with this change the error message will look
like this:

Invalid server address "localhost". The address must be in IPv4 or IPv6 format.

Signed-off-by: Radostin Stoyanov <rstoyanov1@gmail.com>