[tool] Fix backport validator for non-SLURP

non-SLURP branches are EOL'd in case they reach their end of maintained
phase. This could produce a situation when a patch is merged in a
non-SLURP branch that was deleted in the meantime and it's further
backports fail on gate with backport validator as the hash of the
non-SLURP version of the patch is not on any branch.

This patch fixes the above issue as follows: in case a hash is not
found on any branch, then it checks if it can be found under any *-eol
tag and only fails if there is not found either.

Change-Id: I56705bce8ee4354cd5cb1577a520c2d1c525f57b
(cherry picked from commit e383b46)
(cherry picked from commit 8b0ae72)
(cherry picked from commit 88e49dd)
(cherry picked from commit db438e5)
(cherry picked from commit 0fdd21f)
(cherry picked from commit 75497b0)

Author: Elod Illes

tools/check-cherry-picks.sh

@@ -26,8 +26,11 @@ branches+=""
 for hash in $hashes; do
     branch=$(git branch -a --contains "$hash" 2>/dev/null| grep -oE '(master|stable/[a-z0-9.]+|unmaintained/[a-z0-9.]+)')
     if [ $? -ne 0 ]; then
-        echo "Cherry pick hash $hash not on any master, stable or unmaintained branches"
-        exit 1
+        branch=$(git tag --contains "$hash" 2>/dev/null| grep -oE '([0-9.]+-eol)')
+        if [ $? -ne 0 ]; then
+            echo "Cherry pick hash $hash not on any master, stable, unmaintained or EOL'd branches"
+            exit 1
+        fi
     fi
     branches+=" $branch"
     checked=$(($checked + 1))