REGTESTS: ssl: "set ssl cert" and multi-certificates bundle

This test loads a configuration which uses multi-certificates bundle and
tries to change them over the CLI.

Could be backported as far as 2.2, however the 2.2 version must be
adapted to commit the bundle and not each certificate individually.
diff --git a/reg-tests/ssl/cert1-example.com.pem.ecdsa b/reg-tests/ssl/cert1-example.com.pem.ecdsa
new file mode 100644
index 0000000..060d92b
--- /dev/null
+++ b/reg-tests/ssl/cert1-example.com.pem.ecdsa
@@ -0,0 +1,17 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+-----BEGIN PRIVATE KEY-----
+MIG2AgEAMBAGByqGSM49AgEGBSuBBAAiBIGeMIGbAgEBBDCSlVR2c8kUsBYDAqrH
+M60zwqNVVB0FGafWXBJBn4kgTKRQPCqmwkAJp+yd62Z05iKhZANiAARa5/TmNMr0
+TtU18NWScdN2nsUcH4s04xU8H9cFGIuZT/78TMXQP7m3gA+TBri9LDdRyRZQygDE
+6snV1STxPxjkDFYYGiZy4BAa1+ZSUMFe+FSOwnWz1nOLLpbJGRT99yw=
+-----END PRIVATE KEY-----