Ensure that JSch knows HostKeyAlgorithms ssh-rsa and ssh-dss

Without these registrations, JSch's up-front checks which algorithms
are available at all fail if the ssh config explicitly sets only these
algorithms.

Bug: 537790
Change-Id: Idb0431190a7f101913363ee95af6c8fcbda6c923
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

org.eclipse.jgit/src/org/eclipse/jgit/transport/JschConfigSessionFactory.java

@@ -372,6 +372,8 @@ public abstract class JschConfigSessionFactory extends SshSessionFactory {
 	 */
 	protected JSch createDefaultJSch(FS fs) throws JSchException {
 		final JSch jsch = new JSch();
+		JSch.setConfig("ssh-rsa", JSch.getConfig("signature.rsa")); //$NON-NLS-1$ //$NON-NLS-2$
+		JSch.setConfig("ssh-dss", JSch.getConfig("signature.dss")); //$NON-NLS-1$ //$NON-NLS-2$
 		configureJSch(jsch);
 		knownHosts(jsch, fs);
 		identities(jsch, fs);