lower maximum shares per node from 5% to 1.67% (from minimum of 10 mi…

…nutes per share to 30 minutes)

pulled from
p2pool@69d7300
to hopefully resolve error where pool gets stuck on 5% error.

p2pool/work.py

@@ -249,7 +249,7 @@ def get_work(self, pubkey_hash, desired_share_target, desired_pseudoshare_target
             local_hash_rate = self._estimate_local_hash_rate()
             if local_hash_rate is not None:
                 desired_share_target = min(desired_share_target,
-                    bitcoin_data.average_attempts_to_target(local_hash_rate * self.node.net.SHARE_PERIOD / 0.05)) # limit to 5% of pool shares by modulating share difficulty
+                    bitcoin_data.average_attempts_to_target(local_hash_rate * self.node.net.SHARE_PERIOD / 0.0167)) # limit to 1.67% of pool shares by modulating share difficulty
 
             local_addr_rates = self.get_local_addr_rates()
             lookbehind = 3600//self.node.net.SHARE_PERIOD