Workaround Resolv::DNS-induced hangs by installing resolv 0.1.0 (#16157)

See https://github.com/tootsuite/mastodon/pull/16154#issuecomment-832062139

Gemfile

@@ -157,3 +157,5 @@ gem 'concurrent-ruby', require: false
 gem 'connection_pool', require: false
 
 gem 'xorcist', '~> 1.1'
+
+gem 'resolv', '~> 0.1.0'

Gemfile.lock

@@ -498,6 +498,7 @@ GEM
     regexp_parser (2.1.1)
     request_store (1.5.0)
       rack (>= 1.4)
+    resolv (0.1.0)
     responders (3.0.1)
       actionpack (>= 5.0)
       railties (>= 5.0)
@@ -773,6 +774,7 @@ DEPENDENCIES
   rdf-normalize (~> 0.4)
   redis (~> 4.2)
   redis-namespace (~> 1.8)
+  resolv (~> 0.1.0)
   rqrcode (~> 1.2)
   rspec-rails (~> 5.0)
   rspec-sidekiq (~> 3.1)