[Qt] Fix PIV balances on overview page
[Qt] Fix PIV balances on overview page

Locked balances were being double counted in the total and available
values. This fixes the issue once and for all.

fixes #654

PIVX-Project/PIVX,npccoin/npccoin,Darknet-Crypto/Darknet,Mrs-X/Darknet,PIVX-Project/PIVX,Darknet-Crypto/Darknet,Mrs-X/Darknet,PIVX-Project/PIVX,benzmuircroft/REWIRE.io,npccoin/npccoin,Mrs-X/PIVX,npccoin/npccoin,Darknet-Crypto/Darknet,PIVX-Project/PIVX,Mrs-X/Darknet,benzmuircroft/REWIRE.io,PIVX-Project/PIVX,PIVX-Project/PIVX,npccoin/npccoin,benzmuircroft/REWIRE.io,Mrs-X/PIVX,benzmuircroft/REWIRE.io,Mrs-X/Darknet,Mrs-X/PIVX,PIVX-Project/PIVX,Mrs-X/PIVX,benzmuircroft/REWIRE.io,benzmuircroft/REWIRE.io,npccoin/npccoin,Mrs-X/PIVX,Darknet-Crypto/Darknet,Mrs-X/Darknet,Darknet-Crypto/Darknet,PIVX-Project/PIVX,Mrs-X/PIVX,npccoin/npccoin,Mrs-X/Darknet,PIVX-Project/PIVX,Darknet-Crypto/Darknet