Pass cli options to user role's admin_user ping test

[fullyint]

When #578 added connection-related CLI options to the remote-user role's ping command, it probably should have also updated the users role's ping command (introduced in #345). Here is a discourse thread demonstrating the need for this fix.

This PR:

• applies Add connection-related cli options to ping command #578's cli_options_ping to the users role
• removes --user from cli_options_ping, adjusting each task to specify user explicitly, given that the two different ping tests rely on different users
• adds a default for the cli_options_ping variable as a safety in case vars_plugins ever happened to be disabled, in which case the var would be undefined

[swalkinshaw]

👍