cache: Don't send 2 packets as lookup reply
client: Fixed trans number in lookup's trans:cmd
tests: Added 3 more tests about lookup results
route: dnet_add_state() returns either positive number of connected nodes, or negative error

In particular if it failed to connect to any node, it returns -ECONNREFUSED
Merge pull request #497 from shaitan/master

Updates and Fixes
Merge pull request #498 from euroelessar/master

protocol: Lookup fixes and improvements