Fix problem with empty cache after reboot

[ykulazhenkov]

What this PR does / why we need it:
Use /var/lib/cni/ovs-cni/cache dir to store config cache.
Old path /tmp/ovscache is cleaned up after reboot on some operating systems.
Lack of the cache entries may prevent ovs-cni to do a proper cleanup on CmdDel.
Use /var/lib/cni/ovs-cni/cache as a persistent cache dir.

Special notes for your reviewer:

Problem with the current code (before this patch):

1. /tmp/ovscache is used as a cache path by default

   ovs-cni/pkg/utils/cache.go

   Line 29 in 10d2594

   DefaultCacheDir = "/tmp/ovscache"

2. /tmp dir will be cleaned up during the host reboot on some distros
3. CmdDel exit without an error if cache entry not found

   ovs-cni/pkg/plugin/plugin.go

   Line 485 in 10d2594

   return nil

4. ovs-cni will not be able to do a cleanup after the reboot, this will cause, the following state in ovs

d178a096-20dd-4aa1-931a-0a3e82613228
    Bridge mybr
        Port mybr
            Interface mybr
                type: internal
        Port vethd25775b1
            Interface vethd25775b1
                error: "could not open network device vethd25775b1 (No such device)"
    ovs_version: "2.17.9"

5. on next CmdAdd all port with an error will be removed

   ovs-cni/pkg/plugin/plugin.go

   Line 271 in 10d2594

   if err := cleanPorts(ovsDriver); err != nil {

6. for non HW offloading use-case this will fix the issue (symptom, not the root cause)
7. for HW offloading use-case, Ports will have no error and these ports will not be released by the cleanPorts function. As a result VFs will stuck in the OVS and manual clean-up is required before they can be used again.

Release note:

NONE

cc @e0ne @SchSeba

[kubevirt-bot]

Hi @ykulazhenkov. Thanks for your PR.

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[ykulazhenkov]

After discussion with @e0ne we decided that it is better to implement alternative option. I marked PR as draft to apply required changes.

[ykulazhenkov]

After discussion with @e0ne we decided that it is better to implement alternative option. I marked PR as draft to apply required changes.

required changes implemented. The PR is ready for reviews

[SchSeba]

/ok-to-test

[SchSeba]

/lgtm
/approve

[kubevirt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: SchSeba, ykulazhenkov

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[ykulazhenkov]

/test pull-e2e-ovs-cni