WithResult lifecycle state should not rollback trx on exception

Current behaviour:

At AbstractEvalOpProcessor, when we define the withResult lifecycle state, we rollback the transaction if an exception occurred while executing the state. [1]

However, it's the responsibility of afterFailure lifecycle state to handle any failure in prior lifecycle states (such as withResult) and hence, should be the right place to call rollback on a transaction. 

In the current model, the transaction rollback is called twice, once at  [1] and again at  [2]

Proposal

As part of this JIRA, we should remove any transaction handling from the catch block at  [1]i.e. comment out this line: https://github.com/apache/tinkerpop/blob/master/gremlin-server/src/main/java/org/apache/tinkerpop/gremlin/server/op/AbstractEvalOpProcessor.java#L262 

 [1]https://github.com/apache/tinkerpop/blob/master/gremlin-server/src/main/java/org/apache/tinkerpop/gremlin/server/op/AbstractEvalOpProcessor.java#L262

 [2]https://github.com/apache/tinkerpop/blob/3a5917be789612acb31a7043f47f67c6e16b31f6/gremlin-groovy/src/main/java/org/apache/tinkerpop/gremlin/groovy/engine/GremlinExecutor.java#L304