resolv: Use the same default timeout for SRV queries as previously
    
    When we changed the resolver code to use the TTL values from the DNS
    queries instead of harcoded ones, we changed the default value by
    accident.
    
    Add a separate SRV TTL that is backwards-compatible with the old
    harcoded value.
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>