login command forget to scan chain

Causing print balance show wrong after restart bts_wallet.

reproduce(some src modify due to genesis.cfg missing, so using earlier genesis address)
1. start bts_wallet, login, importkey d987064e501555cf3d2e4e68f093a94144bc876a85c520971b747af32fa6a4c3 rescan
2. balence // showing having 100bts
3. quit
4. restart bts_wallet, login
5. balance // wrong, no showing 100bts and unspent output, due to not scan chain.
Merge pull request #54 from HackFisher/patch-3

login command forget to scan chain