message: Only enable/disable PrivacyDialog zPIV elements if needed.
  Currently the zPIV buttons are constantly updated to enabled or disabled even if they are already in the correct state.
diff: @@ -791,7 +791,9 @@ void PrivacyDialog::updateAutomintStatus()
  void PrivacyDialog::updateSPORK16Status()
  {
  // Update/enable labels, buttons and tooltips depending on the current SPORK_16 status
  - if(GetAdjustedTime() > GetSporkValue(SPORK_16_ZEROCOIN_MAINTENANCE_MODE)) {
  + bool fButtonsEnabled = ui->pushButtonMintzPIV->isEnabled();
  + bool fMaintenanceMode = GetAdjustedTime() > GetSporkValue(SPORK_16_ZEROCOIN_MAINTENANCE_MODE);
  + if (fMaintenanceMode && fButtonsEnabled) {
  // Mint zPIV
  ui->pushButtonMintzPIV->setEnabled(false);
  ui->pushButtonMintzPIV->setToolTip(tr("zPIV is currently disabled due to maintenance."));
  @@ -799,8 +801,7 @@ void PrivacyDialog::updateSPORK16Status()
  // Spend zPIV
  ui->pushButtonSpendzPIV->setEnabled(false);
  ui->pushButtonSpendzPIV->setToolTip(tr("zPIV is currently disabled due to maintenance."));
  - }
  - else {
  + } else if (!fMaintenanceMode && !fButtonsEnabled) {
  // Mint zPIV
  ui->pushButtonMintzPIV->setEnabled(true);
  ui->pushButtonMintzPIV->setToolTip(tr("PrivacyDialog", "Enter an amount of PIV to convert to zPIV", 0));
  