Role fails when using lvm_filesystem action

Summary

When trying to run lvm_filesystem action with filesystem_lvm_physical_devices as empty list role fails.

Steps to reproduce

Run action lvm_filesystem on host which do not has installed lvm2 package.

Expected behavior

Role should skip all tasks in action or install necessery package first or fails with appropriate message.

Actual behavior

Role fails on first task.

Possible fixes

1. Add lvm2 package as requierd to role README.
2. Put all lvm_filesystem actions to block and add to it "when" statement which will skip execution if filesystem_lvm_physical_devices list is empty.