ui: Fix check about which images support ssh keys

Fix the check about which images support ssh keys. Besides the operating
system of the image we must also check if the properties of the image
specify that the 'EnforcePersonality' task or all tasks will be
excluded. Also, if the image has no properties, then that it is
equivalent with exclude all tasks.
ui: Add check about which images support password

Add check about which images support setting a new password new
machines. Namely, check if the image has the 'EXCLUDE_ALL_TASKS' or
'EXCLUDE_TASK_CHANGEPASSWORD' image properties.
ui: Hide password when image does not support it

Make the final step of the VM creation wizard to not display the
password of the VM, if it using an image that does not support
setting a password (e.g. snapshots).