initramfs: fix import of additional zpools on boot

Currently all zpools defined in ZFS_INITRD_ADDITIONAL_DATASETS
aren't imported correctly if they are on an other zpool than
the root-pool. The mount fails hence the zpool is not known.
Initramfs asks know for the second decryption-key on boot for
second zpool.

Signed-off-by: theQuestionmark <17354322+theQuestionmark@users.noreply.github.com>

contrib/initramfs/scripts/zfs

@@ -897,6 +897,15 @@ mountroot()
 		ZFS_RPOOL="${pool}"
 	fi
 
+        # We need to import additional zpools which aren't under root zpool, before mount_fs()
+        for add_zpool in $ZFS_INITRD_ADDITIONAL_DATASETS; do
+                add_zpool_base="${add_zpool%%/*}"
+
+                if [ "$add_zpool_base" != "$ZFS_RPOOL" ]
+                then
+                        import_pool "${add_zpool_base}"
+                fi
+        done
 
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