Reduce inefficiency of GetAccountAddress()
Reduce inefficiency of GetAccountAddress()

Don't scan the wallet to see if the current key has been used if we're going to make a new key anyway.
Stop scanning the wallet as soon as we see that the current key has been used.
Don't call isValid() twice on the current key.

robvanmieghem/clams,nochowderforyou/clams,nochowderforyou/clams,nochowderforyou/clams,dooglus/clams,robvanmieghem/clams,Kefkius/clams,nochowderforyou/clams,dooglus/clams,dooglus/clams,robvanmieghem/clams,robvanmieghem/clams,robvanmieghem/clams,dooglus/clams,nochowderforyou/clams,Kefkius/clams,Kefkius/clams,Kefkius/clams,dooglus/clams,Kefkius/clams