properly initialize metaTileEntityTank fluid inventory

[PrototypeTrousers]

What:
Suggested Fix for #1289 and #1263
Separated from PR #1303
those issues happen due to metaTileEntityTank fluid inventory not being properly initialised on load.

How solved:
calling this.fluidInventory = getActualFluidTank();
instead of initializeInventory();

instead of initializeInventory() is a metaTileEntity method that initialize fluidinventory as
this.fluidInventory = new FluidHandlerProxy(importFluids, exportFluids);
but we have neither importFluids nor exportFluids on meta tile entities tanks, leading
to getTankProperties().length being 0, so when the tank is asked by the cover for its capability, null is returned.
Since the pump need the capability to be non null, it crashes

Outcome:
World loading normally

[LAGIdiot]

Thank you for your hard work. But this is just partial copy of functionality from #1303 right? As that one have even proper tank forming on load when cover was placed on it.

[PrototypeTrousers]

Yes, this fixes ONLY the crash, and as its world breaking i thought this part could go first.
there still multiblock issues even with the other PR.
like client-side desync and fluid voiding.
if you rather wait some more, close this PR and i will merge this one with the tank changes when its ready. Thanks :)

[PrototypeTrousers]

closing in favor of #1313