Fix broken pipe from gdb after killing process (#151)

Author: MetalDream666

Diff for: testgres/plugins/pg_probackup2/pg_probackup2/gdb.py

@@ -108,6 +108,9 @@ def kill(self):
         self.proc.stdin.close()
         self.proc.stdout.close()
 
+    def terminate_subprocess(self):
+        self._execute('kill')
+
     def set_breakpoint(self, location):
 
         result = self._execute('break ' + location)