libqtest: only call fclose() on open files

libqtest.c can segfault when calling fclose() if the pidfile wasn't
opened successfully. This patch fixes the issue.

Signed-off-by: Jesse Larrew <jlarrew@linux.vnet.ibm.com>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Message-id: 1367250772-17928-1-git-send-email-jlarrew@linux.vnet.ibm.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

tests/libqtest.c

@@ -99,8 +99,8 @@ static pid_t qtest_qemu_pid(QTestState *s)
         if (fgets(buffer, sizeof(buffer), f)) {
             pid = atoi(buffer);
         }
-    }
         fclose(f);
+    }
     return pid;
 }