1/2: Rename domain "system" to "system_server".

This is a follow-up CL to the extraction of "system_app" domain
from the "system" domain which left the "system" domain encompassing
just the system_server.

Since this change cannot be made atomically across different
repositories, it temporarily adds a typealias "server" pointing to
"system_server". Once all other repositories have been switched to
"system_server", this alias will be removed.

Change-Id: I90a6850603dcf60049963462c5572d36de62bc00
diff --git a/domain.te b/domain.te
index 215c1a3..6321237 100644
--- a/domain.te
+++ b/domain.te
@@ -20,7 +20,7 @@
 
 # Inherit or receive open files from others.
 allow domain init:fd use;
-allow domain system:fd use;
+allow domain system_server:fd use;
 
 # Connect to adbd and use a socket transferred from it.
 allow domain adbd:unix_stream_socket connectto;