[Client] Change how the adapter is set in the client initializer

Migrating to Faraday 1.0 means we check with `adapter` to see which one has been
selected. I also changed the order in which the given block is ran. There's a
case where one of the adapter libraries could be loaded and an adapter is passed
in with the block, but `__auto_detect_adapter` would overwrite this. So the
block is now ran last.

Author: picandocodigo

elasticsearch-transport/lib/elasticsearch/transport/client.rb

@@ -142,10 +142,8 @@ def initialize(arguments={}, &block)
           transport_class  = @arguments[:transport_class] || DEFAULT_TRANSPORT_CLASS
           if transport_class == Transport::HTTP::Faraday
             @transport = transport_class.new(hosts: @seeds, options: @arguments) do |faraday|
-              block.call faraday if block
-              unless (h = faraday.builder.handlers.last) && h.name.start_with?("Faraday::Adapter")
-                faraday.adapter(@arguments[:adapter] || __auto_detect_adapter)
-              end
+              faraday.adapter(@arguments[:adapter] || __auto_detect_adapter)
+              block&.call faraday
             end
           else
             @transport = transport_class.new(hosts: @seeds, options: @arguments)