Refactor resetting gems to a method

This makes it more clear what we're doing with Specification::dirs=

lib/rubygems/server.rb

@@ -445,7 +445,7 @@ def initialize(gem_dirs, port, daemon, launch = nil, addresses = nil)
     @spec_dirs = @gem_dirs.map { |gem_dir| File.join gem_dir, 'specifications' }
     @spec_dirs.reject! { |spec_dir| !File.directory? spec_dir }
 
-    Gem::Specification.dirs = @gem_dirs
+    reset_gems
 
     @have_rdoc_4_plus = nil
   end
@@ -470,7 +470,7 @@ def have_rdoc_4_plus?
   end
 
   def latest_specs(req, res)
-    Gem::Specification.dirs = @gem_dirs
+    reset_gems
 
     res['content-type'] = 'application/x-gzip'
 
@@ -531,7 +531,7 @@ def listen addresses = @addresses
   end
 
   def quick(req, res)
-    Gem::Specification.dirs = @gem_dirs
+    reset_gems
 
     res['content-type'] = 'text/plain'
     add_date res
@@ -567,7 +567,7 @@ def quick(req, res)
   end
 
   def root(req, res)
-    Gem::Specification.dirs = @gem_dirs
+    reset_gems
 
     add_date res
 
@@ -698,6 +698,13 @@ def rdoc(req, res)
     res.body = template.result binding
   end
 
+  ##
+  # Updates the server to use the latest installed gems.
+
+  def reset_gems # :nodoc:
+    Gem::Specification.dirs = @gem_dirs
+  end
+
   ##
   # Returns true and prepares http response, if rdoc for the requested gem
   # name pattern was found.
@@ -788,7 +795,7 @@ def run
   end
 
   def specs(req, res)
-    Gem::Specification.dirs = @gem_dirs
+    reset_gems
 
     add_date res