ssh config parsing: expand ~ in IdentityAgent path

[rufoa]

Currently if a user has an option in their ssh config file like this:
IdentityAgent ~/.1password/agent.sock
then cyberduck can't open the socket because the ~ in the path isn't expanded, it's treated as a literal ~

(But IdentityAgent /Users/myname/.1password/agent.sock works correctly)

This PR applies the same logic to IdentityAgent as is already used for IdentityFile, so paths with ~ work correctly.

Thanks

[CLAassistant]

All committers have signed the CLA.

[dkocher]

Type of identityAgent must be changed accordingly.

[dkocher]

Review usages of getIdentityAgent.

[rufoa]

Is this OK or would you rather move the .getAbbreviatedPath() call to here instead?

cyberduck/ssh/src/main/java/ch/cyberduck/core/sftp/SFTPSession.java

Line 301 in 4ea8d5d

new OpenSSHIdentityAgentConfigurator().getIdentityAgent(host.getHostname()))));

[dkocher]

Can you please sqash the commits to a single commit using rebase -i master.