setInvalid instead of invalidate + strictEqual assert

instead of running this.invalidate which deadlocks the chain, set the hash to invalid manually with this.setInvalid.

update assertion to use strict equal

lib/blockchain/chain.js

@@ -985,11 +985,12 @@ class Chain extends AsyncEmitter {
         // mark invalid_child from tip of fork to first block of fork
         while (indexWalk.height !== fork.height + 1) {
           indexWalk = await this.getPrevious(indexWalk)
-          await this.invalidate(indexWalk.hash)
+          await this.setInvalid(indexWalk.hash)
         }
 
         // check
-        assert.equal(await this.getPrevious(indexWalk), fork, 'nlr invalidation down to the fork')
+        indexWalk = await this.getPrevious(indexWalk)
+        assert.strictEqual(indexWalk, fork)
 
         return true
       }