migration: Plug memory leak in migrate-set-cache-size command

We call g_free() after cache_fini() in migration_end(), but we don't
call it after cache_fini() in xbzrle_cache_resize(), leaking the
memory.

cache_init() and cache_fini() are a pair.  Since cache_init()
allocates the cache, let cache_fini() free it.  This plugs the leak.
Signed-off-by: NChen Gang <gang.chen.5i5j@gmail.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

arch_init.c

@@ -739,7 +739,6 @@ static void migration_end(void)
     XBZRLE_cache_lock();
     if (XBZRLE.cache) {
         cache_fini(XBZRLE.cache);
-        g_free(XBZRLE.cache);
         g_free(XBZRLE.encoded_buf);
         g_free(XBZRLE.current_buf);
         XBZRLE.cache = NULL;

page_cache.c

@@ -109,6 +109,7 @@ void cache_fini(PageCache *cache)
 
     g_free(cache->page_cache);
     cache->page_cache = NULL;
+    g_free(cache);
 }
 
 static size_t cache_get_cache_pos(const PageCache *cache,