Merge branch 'stable-3.4'
* stable-3.4:
HostKeyProvider: Set algorithm to rsa for legacy host key
Honour {httpd,sshd}.gracefulStopTimeout in gerrit.sh
SSH transport: Re-enable weak kex algorithms
Elasticsearch: Discontinue EOL version 7.5 support
Change-Id: If0b996cb18b8fa7cc11a6b33d9b3d1fe5cae07bb