MFH: r532111

security/libssh: Update to 0.9.4

Security release to fix CVE-2020-1730.

Exp-run by: antoine
PR: 245572
Reviewed by: tcberner
Approved by: ports-secteam (blanket bug fix release), gerald (mentor)
Security: CVE-2020-1730
Differential Revision: https://reviews.freebsd.org/D24374