code: boolean isNegotiable(CipherSuite s) {
          if (activeCipherSuites == null) {
              activeCipherSuites = getActiveCipherSuites();
          }
  
          return activeCipherSuites.contains(s) && s.isNegotiable();
      }
docs: Check if the given ciphersuite is enabled and available.
  Does not check if the required server certificates are available.