Call importaddress with param rescan true，then other calls will take so long time #12807

<!-- Describe the issue -->

Call importaddress with param rescan true，then other calls will take so long time，Can‘t response immediately！’

<!--- What behavior did you expect? -->

When i importaddress with param rescan true ，other rpc calls can response immediately！

<!--- What was the actual behavior (provide screenshots if the issue is GUI-related)? -->

Other rpc calls blocked！

<!--- How reliably can you reproduce the issue, what are the steps to do so? -->

Open two terminal,One call importaddress method,another call listaccount method! Then the listaccount will wait long time!

<!-- What version of Bitcoin Core are you using, where did you get it (website, self-compiled, etc)? -->

0.15

<!-- What type of machine are you observing the error on (OS/CPU and disk type)? -->

centos

Yes, this is expected. No wallet operations are possible until the rescan completes.

If you want to import multiple addresses at once, you're better off with the importmulti RPC which can import multiple addresses at the same time, and rescan only once.

@sipa I found that,importmulti can rescan, and rpc call also can response immediately! As long as it is not the request without rescan param‘s value is true！