OVS capabilities test failure masks exception

[Assaf Muller]

neutron/agent/linux/ovs_lib:ofctl_arg_supported executes an ovs-ofctl command and catches the general Exception, concluding that the feature is not supported. However, unexpected exceptions may be raised, swallowed and never logged. So, for example, if an OVS agent starts up and arp_responder is True, then the capabilities test for it may fail in an unexpected way. The result is that arp_responder will not be supported, the agent will start and the exception will not be printed, masking a potential bug.

Additionally, the capability test should be moved to the offline sanity command.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/94839
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=43c1f98f074549611db90b6c333d2c54d7e4d4b3
Submitter: Jenkins
Branch: master

commit 43c1f98f074549611db90b6c333d2c54d7e4d4b3
Author: Assaf Muller <email address hidden>
Date: Thu May 22 14:38:30 2014 +0300

    Move ARP responder test to sanity command

    Additionally, the patch improves the check itself:
    To check if the currently installed OVS supports the ARP responder
    feature, we try to add a flow that references an OpenFlow ARP
    extension via ofctl. The test may fail due to an (expected)
    Runtime error, or due to some other unexpected error.
    In such a case the error was previously masked and tossed away.

    * Clean up ARP responder unit test
    * Extract ARP responder flow actions to be used by the unit
      tests, functional test as well as the ARP responder code itself

    After this patch, if the sanity check returned False but the
    user never ran it or ignored its results, the OVS agent will
    output errors to the log every time an ARP entry is (attempted)
    to be added or removed from the flow table.

    Closes-Bug: #1323718
    Change-Id: I428c954d6561cd398a1e580804a9482969a154af