Remove SSH_AGENT_PID forwarding

This variable plays no role in using the agent for authentication, only
in managing its life-cycle.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/context.py

@@ -103,7 +103,7 @@ class Context:
                             'No default locales set.', distro_bases)
 
         for key in ['http_proxy', 'https_proxy', 'ftp_proxy', 'no_proxy',
-                    'SSH_AGENT_PID', 'SSH_AUTH_SOCK']:
+                    'SSH_AUTH_SOCK']:
             val = os.environ.get(key, None)
             if val:
                 self.environ[key] = val

kas/libkas.py

@@ -261,7 +261,7 @@ def get_build_environ():
         extra_white = env['BB_ENV_EXTRAWHITE'] + ' ' + ' '.join(env_vars)
         env.update({'BB_ENV_EXTRAWHITE': extra_white})
 
-    env_vars.extend(['SSH_AGENT_PID', 'SSH_AUTH_SOCK',
+    env_vars.extend(['SSH_AUTH_SOCK',
                      'SHELL', 'TERM',
                      'GIT_PROXY_COMMAND', 'NO_PROXY'])