MINOR: server: allow init-state for dynamic servers

MINOR: server: allow init-state for dynamic servers

Commit 50322df introduced the init-state keyword, but it didn't enable
it for dynamic servers. However, this feature is perfectly desirable
for virtual servers too, where someone would like a server inlived
through "set server be1/srv1 state ready" to be put out of maintenance
in down state until the next health check succeeds.
At reading the code, it seems that it's only a matter of allowing this
keyword for dynamic servers, as current code path calls
srv_adm_set_ready() which incidentally triggers a call to
_srv_update_status_adm().