Revert "Block signals during RPM transaction processing (RhBug:2127943)"

The fix has unintended consequences.

The solution is not that simple, proper fix is postponed for now.

This reverts commit db833ff.

dnf/base.py

@@ -1028,9 +1028,6 @@ def do_transaction(self, display=()):
  for display_ in cb.displays:
  display_.output = False
 
- # block signals to disallow external interruptions of the transaction
- rpm.blockSignals(True)
-
  self._plugins.run_pre_transaction()
 
  logger.info(_('Running transaction'))
@@ -1048,9 +1045,6 @@ def _pto_callback(action, tsis):
  for msg in dnf.util._post_transaction_output(self, self.transaction, _pto_callback):
  logger.debug(msg)
 
- # unblock signals as we are done with the transaction
- rpm.blockSignals(False)
-
  return tid
 
  def _trans_error_summary(self, errstring):