[addrman] Fix new table bucketing during unserialization

An addrman entry can appear in up to 8 new table buckets. We store this
entry->bucket indexing during shutdown so that on restart we can restore
the entries to their correct buckets.

Commit ec45646 broke the
deserialization code so that each entry could only be put in up to one
new bucket. Fix that.

src/addrman.h

@@ -500,7 +500,9 @@ friend class CAddrManTest;
         nTried -= nLost;
 
         // Store positions in the new table buckets to apply later (if possible).
-        std::map<int, int> entryToBucket; // Represents which entry belonged to which bucket when serializing
+        // An entry may appear in up to ADDRMAN_NEW_BUCKETS_PER_ADDRESS buckets,
+        // so we store all bucket-entry_index pairs to iterate through later.
+        std::vector<std::pair<int, int>> bucket_entries;
 
         for (int bucket = 0; bucket < nUBuckets; bucket++) {
             int nSize = 0;
@@ -509,7 +511,7 @@ friend class CAddrManTest;
                 int nIndex = 0;
                 s >> nIndex;
                 if (nIndex >= 0 && nIndex < nNew) {
-                    entryToBucket[nIndex] = bucket;
+                    bucket_entries.emplace_back(bucket, nIndex);
                 }
             }
         }
@@ -523,9 +525,10 @@ friend class CAddrManTest;
             s >> serialized_asmap_version;
         }
 
-        for (int n = 0; n < nNew; n++) {
-            CAddrInfo &info = mapInfo[n];
-            int bucket = entryToBucket[n];
+        for (auto bucket_entry : bucket_entries) {
+            int bucket{bucket_entry.first};
+            const int n{bucket_entry.second};
+            CAddrInfo& info = mapInfo[n];
             int nUBucketPos = info.GetBucketPosition(nKey, true, bucket);
             if (format >= Format::V2_ASMAP && nUBuckets == ADDRMAN_NEW_BUCKET_COUNT && vvNew[bucket][nUBucketPos] == -1 &&
                 info.nRefCount < ADDRMAN_NEW_BUCKETS_PER_ADDRESS && serialized_asmap_version == supplied_asmap_version) {