GA_get_receive_address address reuse with single-sig accounts

[pavel-kokolemin]

When I call GA_get_receive_address with single-sig liquid account it returns old addresses after some period.
I think that's a bug.

get_next_address function looks correct:

    pub fn get_next_address(&self) -> Result<AddressPointer, Error> {
        let pointer = {
            let store = &mut self.store.write()?;
            let acc_store = store.account_cache_mut(self.account_num)?;
            acc_store.indexes.external += 1;
            acc_store.indexes.external
        };
        ...

but the counter is probably rewritten from the Syncer thread:

impl Syncer {
    pub fn sync(&self, client: &Client) -> Result<HashSet<u32>, Error> {
        ...
                    if let Some(max) = max {
                        if i == 0 {
                            last_used.external = max + batch_count * BATCH_SIZE;
        ...

I'm attaching example program to reproduce the issue.
new_address.py.txt

[pavel-kokolemin]

With this change it works correctly:

                 let mut acc_store = store_write.account_cache_mut(account.num())?;
-                acc_store.indexes = last_used;
+                acc_store.indexes.external =
+                    u32::max(acc_store.indexes.external, last_used.external);
+                acc_store.indexes.internal = last_used.internal;

[pavel-kokolemin]

With this change it works correctly:

                 let mut acc_store = store_write.account_cache_mut(account.num())?;
-                acc_store.indexes = last_used;
+                acc_store.indexes.external =
+                    u32::max(acc_store.indexes.external, last_used.external);
+                acc_store.indexes.internal = last_used.internal;

Found a problem with that change. acc_store.scripts and acc_store.scripts are not properly filled.