For ptytest failures print errno; close pty after testing

Every now and then the PtyTest fails.  A rerun typically fixes it.
Add errno output on tcgetpgrp failure. Close pty after test.

FAIL!  : Konsole::PtyTest::testRunProgram() Compared values are not the same
   Actual   (pty.foregroundProcessGroup()): 0
   Expected (pty.processId())             : 3239