[fix] #11: rule BR_G27 : do not count certs being replayed twice

rfc/0010_Duniter_Blockchain_Protocol_V12.md

@@ -2150,7 +2150,18 @@ For each ENTRY in local MINDEX where `op = 'UPDATE', expired_on = 0`:
 
 For each ENTRY in local MINDEX where `type == 'JOIN' OR type == 'ACTIVE'`:
 
-    ENTRY.enoughCerts = COUNT(GLOBAL_CINDEX[receiver=ENTRY.pub,expired_on=null]) + COUNT(LOCAL_CINDEX[receiver=ENTRY.pub,expired_on=null]) >= sigQty 
+If `HEAD.version >= 12`
+
+    BLOCKCHAIN = REDUCE_BY(GLOBAL_CINDEX[receiver=ENTRY.pub], 'issuer')[expired_on=0]
+    INCOMING = LOCAL_CINDEX[receiver=ENTRY.pub]
+    UNIQUE_ISSUERS = UNIQ(CONCAT(
+        PICK(BLOCKCHAIN, 'issuer'),
+        PICK(INCOMING, 'issuer')))
+    ENTRY.enoughCerts = COUNT(UNIQUE_ISSUERS) >= sigQty
+
+else
+
+    ENTRY.enoughCerts = COUNT(GLOBAL_CINDEX[receiver=ENTRY.pub,expired_on=0]) + COUNT(LOCAL_CINDEX[receiver=ENTRY.pub,expired_on=0]) >= sigQty
 
 > Functionally: any member or newcomer needs `[sigQty]` certifications coming *to* him to be in the WoT