NFS test: rearrange the server tree so we can differentiate NFSv3 vs NFSv4

test/TEST-20-NFS/dhcpd.conf

@@ -13,7 +13,7 @@ subnet 192.168.50.0 netmask 255.255.255.0 {
 
 	group {
 		# NFSv3 root=dhcp or root={/dev/,}nfs, use server-id
-		option root-path "/client";
+		option root-path "/nfs/client";
 
 		host nfs3-1 {
 			hardware ethernet 52:54:00:12:34:00;

test/TEST-20-NFS/exports

@@ -1,3 +1,2 @@
-/       192.168.50.0/24(ro,fsid=0,insecure,no_subtree_check,no_root_squash)
-/client 192.168.50.0/24(ro,insecure,no_subtree_check,no_root_squash)
-
+/nfs		192.168.50.0/24(ro,fsid=0,insecure,no_subtree_check,no_root_squash)
+/nfs/client	192.168.50.0/24(ro,insecure,no_subtree_check,no_root_squash)

test/TEST-20-NFS/test.sh

@@ -99,8 +99,8 @@ test_setup() {
     )
 
     # Make client root inside server root
-    initdir=mnt/client
-    mkdir $initdir
+    initdir=mnt/nfs/client
+    mkdir -p $initdir
 
     (
 	. $basedir/dracut-functions