Add ASSERT_CLI() to a couple of backend handling functions
Add ASSERT_CLI() to a couple of backend handling functions

VBE_Delete() and VBE_Poll() are only safe to call from the CLI
handling thread. Add ASSERT_CLI() to make that explicit.

feld/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache,feld/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache,gquintard/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache