fix: Prevent double jailing

[gr8h]

This PR resolves a bug where a validator can be erroneously listed multiple times in the JAILED_VALIDATORS array.

Steps to Reproduce:

1. A validator initiates a maintenance transaction.
2. The emitInitiateChange function is subsequently called.
3. The validator is listed twice in the JAILED_VALIDATORS list.

This PR is building upon: https://github.com/fuseio/fuse-network/pull/146/files

[sweep-ai[bot]]

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