Consolidate gs deletes

[ilkercelikyilmaz]

Remove allocationmutex lock/unlock from Delete calls since we do have Shutdown state.

[agones-bot]

Build Failed 😱

Build Id: e15e0775-9266-40f0-872e-978630a73ba5

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[agones-bot]

Build Failed 😱

Build Id: 91602979-5117-4483-b0cb-e90b68afbb78

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[aLekSer]

Hello @ilkercelikyilmaz,
I think it is needed to squash commits into one before the merge happens. Please, refer to Contributing Guide.
Also it would be useful to run make test from your /build folder to run tests locally.
Lots of tests are failing cause of the change. For instance:

--- FAIL: TestSyncGameServerSet (0.24s)
    --- FAIL: TestSyncGameServerSet/adding_and_deleting_unhealthy_gameservers (0.12s)
        <autogenerated>:1: 
            	Error Trace:	controller_test.go:320
            	Error:      	Should be true
            	Test:       	TestSyncGameServerSet/adding_and_deleting_unhealthy_gameservers
            	Messages:   	A game servers should have been deleted
    --- FAIL: TestSyncGameServerSet/removing_gamservers (0.12s)
        <autogenerated>:1: 
            	Error Trace:	controller_test.go:345
            	Error:      	Not equal: 
            	            	expected: 5
            	            	actual  : 0