influxdb: its admin password and operator token are its own secrets, so an existing instance's can be accepted

They came from `requires: secret`, minted by the vault — right for a fresh
setup (the image's INIT_* variables read them once), wrong for an instance
that already exists: setup is skipped, the minted values match nothing,
and the provisioner holds a token the server never issued (issue 100).
InfluxDB will not take a chosen token value, so the operator token must be
accepted from the instance (`secret accept ace influxdb admin-token`); the
password can be either. As own secrets both are minted for a fresh install
exactly as before, and accepted where the data already knows them.
Found migrating ace's influxdb.

modules/influxdb/module.json

@@ -11,7 +11,9 @@
     "container-runtime"
   ],
   "own-secrets": {
-    "broker": "/var/lib/mesh/influxdb/broker"
+    "broker": "/var/lib/mesh/influxdb/broker",
+    "admin": "${dir:state}/admin.secret",
+    "admin-token": "${dir:state}/admin-token.secret"
   },
   "listens": [
     {
@@ -124,8 +126,7 @@
     }
   ],
   "requires": [
-    "route",
-    "secret"
+    "route"
   ],
   "contributes": {
     "route": {
@@ -133,12 +134,6 @@
       "endpoint": "api"
     }
   },
-  "secrets": {
-    "secret": {
-      "admin": "${dir:state}/admin.secret",
-      "admin-token": "${dir:state}/admin-token.secret"
-    }
-  },
   "build": {
     "on": [
       {