Support both L1 and L2 contract interfaces

[leszko]

What does this pull request do? Explain your changes. (required)
Use different WithdrawFee contract protocol depending if L1 or L2 is used.

The context for this change is that we have a slight difference in the protocols deployed in L1 (mainnet, rinkeby) and L2 (Arbitrum).

Specific updates (required)
N/A

How did you test each of these updates (required)

1. Rinkeby

./livepeer   -network rinkeby   -ethUrl <RINKEBY_INFRURA_URL>   -orchestrator -transcoder   -currentManifest -pricePerUnit

$ curl http://localhost:7935/orchestratorEarningPoolsForRound?round=45
{"TotalStake":0,"TranscoderRewardCut":0,"TranscoderFeeShare":0,"CumulativeRewardFactor":0,"CumulativeFeeFactor":0}

Withdraw Fees from the client results in

E0124 17:43:22.790598   98098 handlers.go:38] HTTP Response Error 500: could not execute WithdrawFees: execution reverted: no fees to withdraw

2. Arbitrum Test Rinkeby

./livepeer -network arbitrum-one-rinkeby -ethController 0xb709f13ed04a5D8BAd7389504e4f35a68cb6580e -ethUrl https://rinkeby.arbitrum.io/rpc -orchestrator -transcoder -pricePerUnit 0 -ethAcctAddr 0x7E71B5087bc14abd6aF3Bbe2d87Ea0ADC14Ce56F -serviceAddr 127.0.0.1:8935

$ curl http://localhost:7935/orchestratorEarningPoolsForRound?round=45
{"TotalStake":0,"TranscoderRewardCut":0,"TranscoderFeeShare":0,"CumulativeRewardFactor":0,"CumulativeFeeFactor":0}

WithdrawFees called from Livepeer CLI results in.

******************************Eth Transaction******************************

Invoking transaction: "withdrawFees". Inputs: "_recipient: 0x7E71B5087bc14abd6aF3Bbe2d87Ea0ADC14Ce56F  _amount: 0"  Hash: "0x43f2ef05bdd6c9e5128c7ad1293d9560baeb127324c706e553cb04b2fd94a301". 

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Does this pull request close any open issues?
fix https://github.com/livepeer/internal-project-tracking/issues/301

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated

[yondonfu]

LGTM! Will push a small change to remove unnecessary line.

[yondonfu]

I think this can be removed.