[ad-hoc] mirror strategy should prepend deleteOps before both bid and ask ops

[nikhilsaraf]

currently we prepend it at the beginning of each list and then combine the lists.
this is wrong because we could have the following order (few examples):

• deleteSellOps, sellOps, deleteBuyOps, buyOps
• sellOps, deleteBuyOps, buyOps
• deleteBuyOps, buyOps, deleteSellOps, sellOps
• buyOps, deleteSellOps, sellOps
• buyOps, deleteSellOps

What we want is for something like this:

• deleteSellOps, deleteBuyOps, sellOps, buyOps
• deleteBuyOps, sellOps, buyOps
• deleteBuyOps, deleteSellOps, buyOps, sellOps
• deleteSellOps, buyOps, sellOps
• deleteSellOps, buyOps