BUG/MEDIUM: ssl/cli: abort ssl cert is freeing the old store

The "abort ssl cert" command is buggy and removes the current ckch store,
and instances, leading to SNI removal. It must only removes the new one.

This patch also adds a check in set_ssl_cert.vtc and
set_ssl_server_cert.vtc.

Must be backported as far as 2.2.
diff --git a/reg-tests/ssl/set_ssl_cert.vtc b/reg-tests/ssl/set_ssl_cert.vtc
index 0e84058..d6d4526 100644
--- a/reg-tests/ssl/set_ssl_cert.vtc
+++ b/reg-tests/ssl/set_ssl_cert.vtc
@@ -86,3 +86,14 @@
     rxresp
     expect resp.status == 200
 } -run
+
+shell {
+    printf "set ssl cert ${testdir}/common.pem <<\n$(cat ${testdir}/common.pem)\n\n" | socat "${tmpdir}/h1/stats" -
+    echo "abort ssl cert ${testdir}/common.pem" | socat "${tmpdir}/h1/stats" -
+}
+
+haproxy h1 -cli {
+    send "show ssl cert ${testdir}/common.pem"
+    expect ~ ".*SHA1 FingerPrint: A490D069DBAFBEE66DE434BEC34030ADE8BCCBF1"
+}
+