use udev device for ppc prep partition proposal(bsc#1041692)

src/lib/bootloader/stage1_proposal.rb

@@ -5,6 +5,7 @@
 Yast.import "Storage"
 
 require "bootloader/stage1_device"
+require "bootloader/udev_mapping"
 
 module Bootloader
   # Represents object that can set passed stage1 to proposed values.
@@ -198,7 +199,9 @@ class PPC < Stage1Proposal
       def propose
         partition = proposed_prep_partition
         if partition
-          assign_bootloader_device([:custom, partition])
+          # ensure that stage1 device is in udev (bsc#1041692)
+          udev_partition = UdevMapping.to_mountby_device(partition)
+          assign_bootloader_device([:custom, udev_partition])
 
           stage1.activate = !on_gpt?(partition) # do not activate on gpt disks see (bnc#983194)
           stage1.generic_mbr = false

test/stage1_test.rb

@@ -100,6 +100,18 @@
         expect(subject.devices).to eq(["/dev/sda1"])
       end
 
+      it "sets udev link for device" do
+        expect(Yast::Storage).to receive(:GetPartition).with(anything, "/dev/sdc1")
+          .and_return("create" => true)
+
+        expect(Bootloader::UdevMapping).to receive(:to_mountby_device).with("/dev/sdc1")
+          .and_return("/dev/disk/by-id/partition1")
+
+        subject.propose
+
+        expect(subject.devices).to eq(["/dev/disk/by-id/partition1"])
+      end
+
       it "activate partition if it is on DOS partition table" do
         expect(Yast::Storage).to receive(:GetDisk).with(anything, "/dev/sdb1")
           .and_return("label" => "dos")