Updated ibd.sh script to take bitcoind options and then pass them directly to the bitcoind call.

Summary: Updated IBD script to take bitcoind options as parameters and pass them directly to the bitcoind call. Also changed the bitcoind call to not run in the background so the script terminates when finished. Completes T524.

Test Plan:
ibd.sh -assumevalid=0 -checkpoints=0 -disablewallet
Check debug.log and you should find:

2019-02-27T00:16:09Z Validating signatures for all blocks.

2019-02-27T00:16:14Z Wallet disabled!

There should be no log message for checkpoints.

Reviewers: deadalnix, jasonbcox, Fabien, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D2612