qemu.tests: Add a test case for test invalid parameters in nic device

This case is designed to test the qemu behavior when it get invcalid parameters.
Qemu should quit with some warning message but not core dump.
Signed-off-by: NYiqiao Pu <ypu@redhat.com>

qemu/tests/cfg/invalid_parameter.cfg

+- invalid_parameter:
+    virt_test_type = qemu
+    type = invalid_parameter
+    start_vm = no
+    run_invalid_cmd = yes
+    queues = 4
+    failed_reason = "Device 'tap' could not be initialized"
+    vhost = on
+    variants:
+        - fd_vhostfds:
+            tapfds_len = 1
+        - fd_queues:
+            tapfds_len = 1
+            vhostfds_len = 0
+            add_queues = yes
+        - fd_fds:
+            add_tapfd = yes
+            vhostfds_len = 0
+        - fds_vhostfd:
+            vhostfds_len = 1
+        - fds_queues:
+            vhostfds_len = 0
+            add_queues = yes
+        - helper_fd:
+            tapfds_len = 1
+            vhostfds_len = 0
+            helper = /usr/libexec/qemu-bridge-helper
+        - helper_fds:
+            helper = /usr/libexec/qemu-bridge-helper
+            vhostfds_len = 0
+        - helper_vhostfds:
+            tapfds_len = 0
+            helper = /usr/libexec/qemu-bridge-helper
+        - helper_vhostfd:
+            tapfds_len = 0
+            vhostfds_len = 1
+            helper = /usr/libexec/qemu-bridge-helper
+        - helper_queues:
+            add_queues = yes
+            tapfds_len = 0
+            vhostfds_len = 0
+            helper = /usr/libexec/qemu-bridge-helper

qemu/tests/invalid_parameter.py

+import logging
+from autotest.client.shared import error
+from virttest import env_process
+from virttest import virt_vm
+
+
+@error.context_aware
+def run(test, params, env):
+    """
+    Qemu invalid parameter in qemu command line test:
+    1) Try boot up guest with invalid parameters
+    2) Catch the error message shows by qemu process
+
+    :param test: QEMU test object
+    :param params: Dictionary with the test parameters
+    :param env: Dictionary with test environment.
+    """
+    vm_name = params["main_vm"]
+    params['start_vm'] = "yes"
+    try:
+        error.context("Start guest with invalid parameters.")
+        env_process.preprocess_vm(test, params, env, vm_name)
+        vm = env.get_vm(vm_name)
+        vm.destroy()
+        raise error.TestFail("Guest start normally, didn't quit as expect.")
+    except Exception, emsg:
+        error.context("Check guest exit status.")
+        if "(core dumped)" in emsg.reason:
+            raise error.TestFail("Guest core dumped with invalid parameters.")
+        else:
+            logging.info("Guest quit as expect: %s" % emsg.reason)