Add iSCSI targets/LUNs through Pacemaker clusters

Support pcs for zfs-generic to configure iSCSI
targets and LUNs. It uses the targetcli implementation
since it's the default pcs resources and also to
keep compatibility with the rest of the code.

closes #462

examples/zfs-generic-iscsi.yaml

@@ -46,6 +46,7 @@ zfs:
 
 iscsi:
   shareStrategy: "targetCli"
+  #shareStrategy: "pcs"
 
   # https://kifarunix.com/how-to-install-and-configure-iscsi-storage-server-on-ubuntu-18-04/
   # https://kifarunix.com/how-install-and-configure-iscsi-storage-server-on-centos-7/
@@ -77,6 +78,17 @@ iscsi:
       attributes:
         # set to 1 to enable Thin Provisioning Unmap
         emulate_tpu: 0
+
+  shareStrategyPcs:
+    #sudoEnabled: true
+    pcs_group: "group-nas"
+    basename: "iqn.2003-01.org.linux-iscsi.ubuntu-19.x8664"
+    auth:
+      enabled: 0
+      # CHAP – incoming only, mutual not supported by the Pacemaker resource agent
+      incoming_username: "foo"
+      incoming_password: "bar"
+
   targetPortal: "server[:port]"
   # for multipath
   targetPortals: [] # [ "server[:port]", "server[:port]", ... ]