modem: Identify modems by sysfs path instead of ofono dbus path

ofono dbus paths are non-deterministic and can change over time for a
given modem. For instance when ofono is restartd or if a modem crashes
and the object is destroyed and re-announced by udev.

Requires at least ofono 1df92289d4e09a1e2db0b189b5153a4c238f98f1, which
implemented the feature to export the sysfs path to modem properties.

Related: OS#2509

Change-Id: Ibc45a196abadded2706dc9d57b6a3a796b43a201
diff --git a/example/resources.conf b/example/resources.conf
index ce370a6..fb2ac9f 100644
--- a/example/resources.conf
+++ b/example/resources.conf
@@ -67,16 +67,16 @@
     band: GSM-1900
 
 modem:
-- label: sierra_1
-  path: '/sierra_1'
+- label: sierra_1st
+  path: '/sys/devices/pci0000:00/0000:00:12.2/usb1/1-1/1-1.2'
   imsi: '901700000009031'
   ki: '80A37E6FDEA931EAC92FFA5F671EFEAD'
   auth_algo: 'comp128v1'
   ciphers: [a5_0, a5_1]
   features: ['sms', 'voice', 'ussd', 'gprs']
 
-- label: sierra_2
-  path: '/sierra_2'
+- label: sierra_2nd
+  path: '/sys/devices/pci0000:00/0000:00:12.2/usb1/1-1/1-1.3'
   imsi: '901700000009029'
   ki: '00969E283349D354A8239E877F2E0866'
   auth_algo: 'comp128v1'
@@ -84,7 +84,7 @@
   features: ['sms', 'voice', 'ussd', 'gprs']
 
 - label: ec20
-  path: '/gobi_0'
+  path: '/sys/devices/pci0000:00/0000:00:12.2/usb1/1-1/1-1.6'
   imsi: '901700000009030'
   ki: 'BB70807226393CDBAC8DD3439FF54252'
   auth_algo: 'comp128v1'
@@ -92,7 +92,7 @@
   features: ['sms', 'ussd', 'gprs']
 
 - label: gobi2k
-  path: '/gobi_3'
+  path: '/sys/devices/pci0000:00/0000:00:12.2/usb1/1-1/1-1.5'
   imsi: '901700000009032'
   ki: '2F70DCA43C45ACB97E947FDD0C7CA30A'
   auth_algo: 'comp128v1'