CI: github: split ssl lib selection based on git branch

CI: github: split ssl lib selection based on git branch

when *SSL_VERSION="latest" behaviour was introduced, it seems to be fine
for development branches, but too intrusive for stable branches.

let us limit "latest" semantic only for development builds, if branch name
contains "haproxy-" it is supposed to be stable branch, no latest openssl
should be taken

[wla: must be backported as far as 2.6]
Signed-off-by: William Lallemand <wlallemand@haproxy.org>