Fix cast errors with clang

Fix cast errors with clang

Build with clang fails with:

  CC       util/libvirt_util_la-virsocketaddr.lo
util/virsocketaddr.c:904:17: error: cast from 'struct sockaddr *' to
'struct sockaddr_in *' increases required alignment from 1 to 4
[-Werror,-Wcast-align]
        inet4 = (struct sockaddr_in*) res->ai_addr;
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
util/virsocketaddr.c:909:17: error: cast from 'struct sockaddr *' to
'struct sockaddr_in6 *' increases required alignment from 1 to 4
[-Werror,-Wcast-align]
        inet6 = (struct sockaddr_in6*) res->ai_addr;
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 errors generated.

Fix that by replacing virSocketAddrParseInternal() call with
virSocketAddrParse() in the virSocketAddrIsNumericLocalhost() function.
virSocketAddrParse stores an address in virSocketAddr.
virSocketAddr uses a union to store an address, so it doesn't
need casting.