Context variables not included in final singed transaction's toJson method

[scalahub]

When we create a transaction with some inputs having context variables set via withContextVar, the following behaviour is observed:

1. The method tx.toJson does not include context variables.
2. When we finally broadcast the transaction, an error is encountered if the script uses context variables.

The above indicates that while the context variables are used in signing, they may not be included in the final transaction.