t/215-layout-restore-crash: fix test description
run con_fix_percent unconditionally, not only on parsing errors
fix killing placeholder windows

The only consequence of the previous situation was that there was a
misleading log message.
Revert "use designated initializers for yajl_callbacks struct"

This reverts commit 705b43294add2fffede086c0c072dc5a849ffc49.

This commit broke i3bar for some users.