[linux-agent] Remove gnome-keyring dependency and drop-in files

[ptitdoc]

Qubes OS version (e.g., R3.2):

R3.2

Affected TemplateVMs (e.g., fedora-23, if applicable):

All

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Expected behavior:

• Cleanup files that are not used anymore in linux-agent
• Document default installed ssh agent in template, and usage in QubesOS (could be superseeded by split-ssh in the future ?)

Actual behavior:

Gnome keyring is installed in all templates as a dependency of linux-agent and files related to gnome-keyring are installed (drop-ins).

General notes:

See dicussion in #2351

Related issues:

#2351
#1962

[ptitdoc]

Concerning the documentation, if gnome-keyring is installed and automatically started, the easiest thing to make it working is to create the file /etc/profile.d/ssh-agent.sh:
export SSH_AUTH_SOCK=/run/user/1000/keyring/ssh

[ptitdoc]

Concerning the documentation, if gnome-keyring is installed and automatically started, the easiest thing to make it working is to create the file /etc/profile.d/ssh-agent.sh:
export SSH_AUTH_SOCK=/run/user/1000/keyring/ssh