Git sync fix (#5776)

Currently when user try to open the task with git repository connected
he will see this (screenshot)

![2023-02-27_17-01](https://user-images.githubusercontent.com/57707673/221584442-329c8592-6524-4715-9c76-7631553dc135.png)
This happens after first synchronization and reloading the page. The
cause of this is ssh-agent, that is not running in cvat_server
container.
This PR will enable ssh-agent on cvat_server so this issue disappears.

supervisord/server.conf

@@ -21,6 +21,13 @@ childlogdir=%(ENV_HOME)s/logs/            ; where child log files will live
 command=bash -c "if [ \"${CLAM_AV}\" = 'yes' ]; then /usr/bin/freshclam -d \
     -l %(ENV_HOME)s/logs/freshclam.log --foreground=true; fi"
 
+
+[program:ssh-agent]
+command=bash -c "rm /tmp/ssh-agent.sock -f && /usr/bin/ssh-agent -d -a /tmp/ssh-agent.sock"
+priority=1
+autorestart=true
+
+
 [program:runserver]
 ; Here need to run a couple of commands to initialize DB and copy static files.
 ; We cannot initialize DB on build because the DB should be online. Also some
@@ -34,4 +41,7 @@ command=%(ENV_HOME)s/wait-for-it.sh %(ENV_CVAT_POSTGRES_HOST)s:5432 -t 0 -- bash
     --limit-request-body 1073741824 --log-level INFO --include-file ~/mod_wsgi.conf \
     %(ENV_DJANGO_MODWSGI_EXTRA_ARGS)s --locale %(ENV_LC_ALL)s \
     --server-root /tmp/cvat-server"
+
+
+environment=SSH_AUTH_SOCK="/tmp/ssh-agent.sock"
 numprocs=%(ENV_NUMPROCS)s