Remove duplicates in ab_partitions.txt am: 34c711a0bd am: c4b29b8f79
am: e08cdbf2e1

Change-Id: I65bf32559fcc89494862356800e976ce7dc0d79e
diff --git a/scripts/brillo_update_payload b/scripts/brillo_update_payload
index f337459..65c63f5 100755
--- a/scripts/brillo_update_payload
+++ b/scripts/brillo_update_payload
@@ -401,7 +401,8 @@
     if grep -v -E '^[a-zA-Z0-9_-]*$' "${ab_partitions_list}" >&2; then
       die "Invalid partition names found in the partition list."
     fi
-    partitions=($(cat "${ab_partitions_list}"))
+    # Get partition list without duplicates.
+    partitions=($(awk '!seen[$0]++' "${ab_partitions_list}"))
     if [[ ${#partitions[@]} -eq 0 ]]; then
       die "The list of partitions is empty. Can't generate a payload."
     fi