Implement be-removable argument to CLI wait. This is implemented via
be_check_for_deletion() invokation, also used by "del backend" handler.
The objective is to test whether a backend instance can be removed. If
this is not the case, the command may returns immediately if the target
proxy is incompatible with dynamic removal or if a user action is
required. Else, the command will wait until the temporary restriction is
lifted.
98c8c5e16e
