CCBC-1667: do not schedule config update during instance termination

Change-Id: I8f6fdfe2ffcf4f7dbcdcc48a9a80d92e6aeba294
Reviewed-on: https://review.couchbase.org/c/libcouchbase/+/231863
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Build Bot <build@couchbase.com>

Author: avsej

src/bucketconfig/bc_cccp.cc

@@ -295,6 +295,9 @@ lcb_STATUS CccpProvider::mcio_error(lcb_STATUS err)
         parent->provider_failed(this, err);
         return err;
     }
+    if (instance->destroying) {
+        return err;
+    }
     return schedule_next_request(err, /* can_rollover */ false, /* skip_if_push_supported */ false);
 }