Volumed data setup changed to allow #1759

- Volumed subfolder now created up in the ENTRYPOINT script, this way
  they are created before S6 even starts making VOLUME.
- The subfolder will be created during VOLUME creation too as ENTRYPOINT
  script will be run before /bin/true
- SSH Keys will now be created on a single key basis not replying on the
  existence of /data/ssh folder

docker/s6/openssh/setup

@@ -1,12 +1,26 @@
 #!/bin/sh
 
-if ! test -d /data/ssh; then
-    mkdir -p /data/ssh
+# Check if host keys are present, else create them
+if ! test -d /data/ssh/ssh_host_key; then
     ssh-keygen -q -f /data/ssh/ssh_host_key -N '' -t rsa1
-    ssh-keygen -q -f /data/ssh/ssh_host_rsa_key -N '' -t rsa
-    ssh-keygen -q -f /data/ssh/ssh_host_dsa_key -N '' -t dsa
-    ssh-keygen -q -f /data/ssh/ssh_host_ecdsa_key -N '' -t ecdsa
-    ssh-keygen -q -f /data/ssh/ssh_host_ed25519_key -N '' -t ed25519
-    chown -R root:root /data/ssh/*
-    chmod 600 /data/ssh/*
 fi
+
+if ! test -d /data/ssh/ssh_host_rsa_key; then
+    ssh-keygen -q -f /data/ssh/ssh_host_rsa_key -N '' -t rsa
+fi
+
+if ! test -d /data/ssh/ssh_host_dsa_key; then
+    ssh-keygen -q -f /data/ssh/ssh_host_dsa_key -N '' -t dsa
+fi
+
+if ! test -d /data/ssh/ssh_host_ecdsa_key; then
+    ssh-keygen -q -f /data/ssh/ssh_host_ecdsa_key -N '' -t ecdsa
+fi
+
+if ! test -d /data/ssh/ssh_host_ed25519_key; then
+    ssh-keygen -q -f /data/ssh/ssh_host_ed25519_key -N '' -t ed25519
+fi
+
+# Set correct right to ssh keys
+chown -R root:root /data/ssh/*
+chmod 600 /data/ssh/*