qemu.py: don't launch again before shutdown()

If a VM is launched, files are created and a cleanup is required before
a new launch. This cleanup is executed by shutdown(), so shutdown() must
be called even if the VM is manually terminated (i.e. using kill).

This patch creates a control to make sure launch() will not be executed
again if shutdown() is not called after the previous launch().

Signed-off-by: Amador Pahim <apahim@redhat.com>
Message-Id: <20180122205033.24893-7-apahim@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

scripts/qemu.py

@@ -90,6 +90,7 @@ class QEMUMachine(object):
         self._qemu_full_args = None
         self._test_dir = test_dir
         self._temp_dir = None
+        self._launched = False
 
         # just in case logging wasn't configured by the main script:
         logging.basicConfig()
@@ -210,10 +211,15 @@ class QEMUMachine(object):
         Launch the VM and make sure we cleanup and expose the
         command line/output in case of exception
         """
+
+        if self._launched:
+            raise QEMUMachineError('VM already launched')
+
         self._iolog = None
         self._qemu_full_args = None
         try:
             self._launch()
+            self._launched = True
         except:
             self.shutdown()
 
@@ -266,6 +272,8 @@ class QEMUMachine(object):
                 command = ''
             LOG.warn(msg, exitcode, command)
 
+        self._launched = False
+
     def qmp(self, cmd, conv_keys=True, **args):
         '''Invoke a QMP command and return the response dict'''
         qmp_args = dict()