dist: Fix '--developer-mode' parsing in scylla_io_setup
dist: Fix '--developer-mode' parsing in scylla_io_setup

We need to support the following variations:

   --developer-mode true
   --developer-mode 1
   --developer-mode=true
   --developer-mode=1

Fixes #1026.
Message-Id: <cbe1831d5fdc7e0b3465d8e0bcdffc6e188a0696@scylladb.com>

duarten/scylla,scylladb/scylla,raphaelsc/scylla,kjniemi/scylla,duarten/scylla,scylladb/scylla,avikivity/scylla,raphaelsc/scylla,avikivity/scylla,duarten/scylla,kjniemi/scylla,kjniemi/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,raphaelsc/scylla