tests: don't try to test unix sockets on vfat

tests/test-commandserver.t

@@ -557,7 +557,7 b' unix domain socket:'
   $ cd repo
   $ hg update -q
 
-#if unix-socket
+#if unix-socket unix-permissions
 
   >>> import cStringIO
   >>> from hgclient import unixserver, readchannel, runcommand, check
@@ -602,8 +602,8 b' unix domain socket:'
   listening at .hg/server.sock
   abort: unknown command unknowncommand
   killed!
-
-#else
+#endif
+#if no-unix-socket
 
   $ hg serve --cmdserver unix -a .hg/server.sock
   abort: unsupported platform