Change linux default network-mode to user

[lilyLuLiu]

Currently, the Linux default network mode is system. But many issues happen due to different system situations.
For most user, user network mode already satisfied their demands. And user network mode no need to deal with complex system situations.
So after discuss, it's better to set user as default network-mode, making sure CRC works well in default.
If the user requires more functions, they can switch to system network mode.

@gbraad @praveenkumar @anjannath have agreed on this being needed.
It needs to start testing early during December.
In the worst case, we can revert before the new release in January.

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[rohanKanojia]

@lilyLuLiu : Hello, Could you please provide some context on why this change is needed?

[praveenkumar]

/retest

[praveenkumar]

@lilyLuLiu About integration failure I think https://github.com/crc-org/crc/blob/main/pkg/crc/network/types.go#L65 is culprit because settings only apply if we build binary for non installer, we need to change the default here also

[openshift-ci]

@lilyLuLiu: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/integration-crc	6b1ce3f	link	true	/test integration-crc
ci/prow/e2e-crc	6b1ce3f	link	true	/test e2e-crc

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