Fixing route-operator not processing tunnelendpoints.net.liqo.io resources on restart

[alacuku]

Description

This PR fixes the route-operator not processing tunnelendpoints.net.liqo.io resources when restarted.
When the operator proccessed a tunnelendpoints.net.liqo.io instance it added a label to the resource to say that it has been processed. Each time the reconcile function of the operator is called upon an update event of the resource it checks if the label is present if yes it would do nothing. This label prevents also the operator to reconcile the state of a resource according to the resyncPeriod. The resyncPeriod is really important to check that the routes and iptables rules have not been modified by an external actor.
This check was introduced to sync the various operators that handled a tunnelendpoints.net.liqo.io resource.
Fixes #264

How Has This Been Tested?

Restarting the route-operator pod and verifying that:

1. liqo-routes are not present while the route-operator is not running
2. liqo-routes are installed after the restart

[coveralls]

Pull Request Test Coverage Report for Build 257686174

• 6 of 11 (54.55%) changed or added relevant lines in 1 file are covered.
• 9 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.02%) to 50.709%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/liqonet/route-operator.go	6	11	54.55%

Files with Coverage Reduction	New Missed Lines	%
internal/liqonet/route-operator.go	1	74.4%
internal/peering-request-operator/peering-request-controller.go	3	69.39%
internal/peering-request-operator/foreign-cluster.go	5	78.43%

Totals
Change from base Build 257595195:	0.02%
Covered Lines:	6726
Relevant Lines:	13264

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💛 - Coveralls

[palexster]

/lgtm
My 2 cents: Can you please explain what you did in this PR and what was the problem?

[mlavacca]

/rebase

[adamjensenbot]

Rebase status: success!