Fix liquidity orders on rinkeby

[Velenir]

The issue happens because:

1. Page load
2. No connection => default networkId = 1
3. selectedTokensMap is filled with tokens from network 1
4. Connection to rinkeby established
5. Tokens updated
6. But selectedTokensMap not refilled

This is a quick fix, but let's switch to addresses instead of symbols soonish.
Having addresses in LIQUIDITY_TOKEN_LIST and that list differentiating by network would have made this issue more obvious (cause there would not have been a match for wrong address on the right network)

Closes #1235

[ghost]

Travis automatic deployment:
https://pr1238--dexreact.review.gnosisdev.com

[alfetopito]

Working like a charm!

[W3stside]

good fix!