Fix default options and updating key

:password_prompt and :logger options are added in net-ssh
`Net::SSH.assign_defaults`.
Set default options early for ConnectionPool cache key.
The key in Cache object should be updated for comparing next time.

lib/sshkit/backends/connection_pool.rb

@@ -122,6 +122,7 @@ def update_key_if_args_changed(cache, args)
 
     caches.synchronize do
       caches[new_key] = caches.delete(cache.key)
+      cache.key = new_key
     end
   end
 

lib/sshkit/backends/connection_pool/cache.rb

@@ -1,7 +1,7 @@
 # A Cache holds connections for a given key. Each connection is stored along
 # with an expiration time so that its idle duration can be measured.
 class SSHKit::Backend::ConnectionPool::Cache
-  attr_reader :key
+  attr_accessor :key
 
   def initialize(key, idle_timeout, closer)
     @key = key

lib/sshkit/backends/netssh.rb

@@ -36,12 +36,20 @@ def ssh_options
         if Net::SSH::VALID_OPTIONS.include?(:known_hosts)
           def default_options
             @default_options ||= {known_hosts: SSHKit::Backend::Netssh::KnownHosts.new}
+            assign_defaults
           end
         else
           def default_options
             @default_options ||= {}
+            assign_defaults
           end
         end
+
+        # Set default options early for ConnectionPool cache key
+        def assign_defaults
+          Net::SSH.assign_defaults(@default_options)
+          @default_options
+        end
       end
 
       def upload!(local, remote, options = {})