Depend on /cfg mount in units which access it

Change-Id: I218b52d2adc8979bca9bde52e22d799165e5a6d1
diff --git a/package/czechlight-cfg-fs/netopeer2-keystored-persistent-keys.service b/package/czechlight-cfg-fs/netopeer2-keystored-persistent-keys.service
index 177c247..76f620e 100644
--- a/package/czechlight-cfg-fs/netopeer2-keystored-persistent-keys.service
+++ b/package/czechlight-cfg-fs/netopeer2-keystored-persistent-keys.service
@@ -1,7 +1,7 @@
 [Unit]
 Description=Store SSH host keys into /cfg
-After=netopeer2-keystored-init-keys.service
-Requires=netopeer2-keystored-init-keys.service
+After=netopeer2-keystored-init-keys.service cfg.mount
+Requires=netopeer2-keystored-init-keys.service cfg.mount
 ConditionPathExists=!/cfg/etc/keystored/keys
 
 [Service]