CLEANUP: mworker: remove the type field in mworker_proc

Since the introduction of the options field, we can use it to store the
type of process.

type = 'm' is replaced by PROC_O_TYPE_MASTER
type = 'w' is replaced by PROC_O_TYPE_WORKER
type = 'e' is replaced by PROC_O_TYPE_PROG

The old values are still used in the HAPROXY_PROCESSES environment
variable to pass the information during a reload.
5 files changed