Adding multipath-tools package for nova hosts

This fix adds the multipath-tools package to all nova
nodes in order to support iscsi-multipath inside nova.

In order to enable this feature in nova the following override
needs to be configured:

nova_nova_conf_overrides:
  libvirt:
    iscsi_use_multipath: true

DocImpact
Closes-Bug: #1524957

Change-Id: I36da282043ce864c8a1fb69a1ee02e3a273c14e4

defaults/main.yml

@@ -290,6 +290,7 @@ nova_compute_kvm_apt_packages:
   - nfs-common
   - dosfstools
   - dosfstools-dbg
+  - multipath-tools
 
 # nova packages that must be installed before anything else
 nova_requires_pip_packages: