Fix crash when a deferred command destroys a workspace
Fix crash when a deferred command destroys a workspace

Example config that produces the crash (with a single output):

    workspace 1
    workspace 2

Prior to this commit, container_workspace_free would manually mark the
L_FLOATING container as destroying and free it. This assumed the
L_FLOATING container would never be involved in a transaction. This was
a safe assumption when it was implemented, but became an incorrect
assumption once parent/child relationships became transactionised.

This commit removes the L_FLOATING free from container_workspace_free.
When the workspace is destroyed, it starts the normal destroy process on
the L_FLOATING container so it can be freed via transactions.

SirCmpwn/sway,taiyu-len/sway,taiyu-len/sway,1ace/sway,1ace/sway,ascent12/sway,1ace/sway,ascent12/sway,ascent12/sway,taiyu-len/sway