Mainnet Release v2.1.1

This is the major release after the mainnet open staking launch release.
It includes protocol enhancement and an important EPoS change.

The changes included in this release since v2.1.0.

• undelegation unlocking epoch from 7 to 0 (undelegation will be locked only within the current epoch and will be unlocked at the end of current epoch), starting from epoch 191, the full proposal in the forum: https://talk.harmony.one/t/proposal-shortening-of-undelegation-locking-period/634
• APR calculation fix and return all APR values in validator information query
• fix of a few nil pointer crashes
• node.sh cleanup and randomize the auto-update time between 5~10 minutes
• cross-link verification time optimization using cache
• txpool error report fix
• increase number of message handlers to reduce the consensus latency

The released version of this release:

node.sh: v1 20200521.0
harmony binary: v5977-v2.1.1-0-g2f8b53b0