qemurunner.py: add try/except for pid handling race

In some instances, attempts to remove the qemu pidfile within the
stop() method fail despite the os.path.exists() call immediately
before implying that the file is present. Add a try/except block
to log a warning if this occurs, rather than failing outright,
since the process simply appears to be exiting at an inconvenient
time.

[YOCTO #13675]

(From OE-Core rev: 0e94cfb4aa718b4842f608879b77d5671b5bf338)

Signed-off-by: Trevor Gamblin <trevor.gamblin@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit eadb899e23b18eb9eaff145c3bf5b20fb417c3e8)
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/utils/qemurunner.py

@@ -396,7 +396,10 @@ class QemuRunner:
         self.qemupid = None
         self.ip = None
         if os.path.exists(self.qemu_pidfile):
-            os.remove(self.qemu_pidfile)
+            try:
+                os.remove(self.qemu_pidfile)
+            except FileNotFoundError as e:
+                self.logger.warning('qemu pidfile is no longer present')
         if self.monitorpipe:
             self.monitorpipe.close()