jsonrpc: Rescan with server ctx not background ctx

Using the server context instead of context.Background means that the
long-lived rescan funcs are able to exit properly when the server is
shutdown and its context is closed.

internal/rpc/jsonrpc/methods.go

@@ -2038,7 +2038,8 @@ func (s *Server) importPrivKey(ctx context.Context, icmd any) (any, error) {
  s.wg.Add(1)
  go func() {
  defer s.wg.Done()
- _ = w.RescanFromHeight(context.Background(), n, scanFrom)
+ serverCtx := s.httpServer.BaseContext(nil)
+ _ = w.RescanFromHeight(serverCtx, n, scanFrom)
  }()
  }
 
@@ -2095,7 +2096,8 @@ func (s *Server) importPubKey(ctx context.Context, icmd any) (any, error) {
  s.wg.Add(1)
  go func() {
  defer s.wg.Done()
- _ = w.RescanFromHeight(context.Background(), n, scanFrom)
+ serverCtx := s.httpServer.BaseContext(nil)
+ _ = w.RescanFromHeight(serverCtx, n, scanFrom)
  }()
  }
 
@@ -2146,7 +2148,8 @@ func (s *Server) importScript(ctx context.Context, icmd any) (any, error) {
  s.wg.Add(1)
  go func() {
  defer s.wg.Done()
- _ = w.RescanFromHeight(context.Background(), n, scanFrom)
+ serverCtx := s.httpServer.BaseContext(nil)
+ _ = w.RescanFromHeight(serverCtx, n, scanFrom)
  }()
  }