CI: adopt openssl download script to download all versions

with recent change, OpenSSL download URL was changed in
incompatiable way. i.e. only the most recent openssl version
might be downloaded using previous script.

older versions are available under different URLs. as we need
several openssl versions, let us adopt script accordingly.

bug was caught after travis-ci cache was purged for some reason.
diff --git a/scripts/build-ssl.sh b/scripts/build-ssl.sh
index 60b876c..0940f3c 100755
--- a/scripts/build-ssl.sh
+++ b/scripts/build-ssl.sh
@@ -3,8 +3,17 @@
 
 download_openssl () {
     if [ ! -f "download-cache/openssl-${OPENSSL_VERSION}.tar.gz" ]; then
+
+#
+# OpenSSL has different links for latest and previous releases
+# since we want to download several versions, let us try to treat
+# current version as latest, if it fails, follow with previous
+#
+
+	wget -P download-cache/ \
+	    "https://www.openssl.org/source/openssl-${OPENSSL_VERSION}.tar.gz" || \
         wget -P download-cache/ \
-            "https://www.openssl.org/source/openssl-${OPENSSL_VERSION}.tar.gz"
+            "https://www.openssl.org/source/old/${OPENSSL_VERSION%[a-z]}/openssl-${OPENSSL_VERSION}.tar.gz"
     fi
 }