Don't open the control socket until after the server socket is bound

This makes it easier for the tests (and supervisor) to guarantee to be
able to connect to the server socket.

Also this patch moves freeing the mirror supervisor into the server
thread.

Rakefile

@@ -24,8 +24,8 @@ CCFLAGS = %w(
              -Wno-missing-field-initializers
             ) + # Added -Wno-missing-field-initializers to shut GCC up over {0} struct initialisers
             [ENV['CFLAGS']]
-            
-LIBCHECK = File.exists?("/usr/lib/libcheck.a") ? 
+
+LIBCHECK = File.exists?("/usr/lib/libcheck.a") ?
   "/usr/lib/libcheck.a" :
   "/usr/local/lib/libcheck.a"
 
@@ -210,11 +210,13 @@ file check("flexnbd") =>
   gcc_link t.name, t.prerequisites + [LIBCHECK]
 end
 
+
 file check("control") =>
   %w{build/tests/check_control.o} + OBJECTS - ["build/main.o"] do |t|
   gcc_link t.name, t.prerequisites + [LIBCHECK]
 end
 
+
 (TEST_MODULES- %w{control flexnbd acl client serve readwrite util}).each do |m|
   tgt = "build/tests/check_#{m}.o"
   maybe_obj_name = "build/#{m}.o"