contracts: initial fixes for delegation tests + staking.sol #878

Job	Run time
test-client-go	1m 0s
test-rust	6m 14s
test-client-js	1m 13s
test-rust-sgx	3m 10s
test-integration-hardhat	41s
test-examples (hardhat)	1m 17s
test-examples (hardhat-boilerplate)	1m 22s
test-examples (onchain-signer)	48s
test-examples (truffle)	53s
test-examples (truffle, 5.8.2)	1m 48s
test-examples (truffle, 5.10.1)	1m 3s
	19m 29s

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