Resolve "Confirm contractor only calls proto package under lock"

Closes #3187 (closed)

I believe this TODO has been resolved. Below are the non contractor package references while the contractor lock is being held.

Calls Found while under Lock

• UnlockHash() (types package)
• Metadata() (proto package)

Other Modules Used while under Lock

• []modules.RenterContract
• modules.Allowance{}
• proto.ContractParams{}