If you do not want to do a short sale but still want to move, then your only other option would be to rent it out or keep it as a second home. If you rent it out, you will not be able to use the rental income to qualify for the next mortgage. You must be able to carry both mortgages and stay within the debt-to-income ratios on your next mortgage.
I would check to see how much rent you can get for this house and how much of the payment it would cover. The advantage of renting is in time the house will be paid off, at least partially by a renter. The disadvantage is the rent may be to low for your expenses and you have to deal with a renter and still manage the maintenance of the house.
And, if you CAN find someone who will pay your second and allow you to keep it as unsecured debt, or if your current lender will do that, that's also a good idea. There are investors who will buy up small loans like that and allow you to pay the loan off with interest. Just know, like any other unsecured debt, there will be terms you must adhere to and if you don't, it could go to collection.
You are on target, by taking a course of trying to avoid a "short sale." Doing so would have a very poor impact on your credit.
We would echo Dan's earlier comment, that possibly renting the townhome until a more beneficial time to sell presents itself, is an option. The down side of this is he waiting period is unclear at best and could be longer that you care to wait.
Your best approach may be to do your best to minimize the difference between the amount owed and what the property would sell for and pay the difference hoping to benefit from finding a real savings on your new purchase. Many people in your situation find comfort in realizing losing on one transaction while saving on the next, at times, can be percieved as a "wash!"