adds two new plugins that use ansible-connection for persistence (#18572)

* adds new connection plugin `network_cli` which builds on paramiko
* adds new plugin `terminal` used for manipulating network_cli terminals
* adds new field to play_context `network_os` settable as ansible_network_os

This commit adds the plugins necesary to establish a persistent cli connection
to network devices of ssh.  It builds on the paramiko connection plugin
to create a shell environment that will persistent through ansible-connection.
The `newtork_cli` plugin then uses the network_os in the instance of
PlayContext to load the appropriate network OS environment plugin for
handling opening and closing of shells as well as privilege escalation.

lib/ansible/plugins/terminal/nxos.py

@@ -0,0 +1,56 @@
+#
+# (c) 2016 Red Hat Inc.
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+#
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+import re
+
+from ansible.plugins.terminal import TerminalBase
+from ansible.errors import AnsibleConnectionFailure
+
+
+class TerminalModule(TerminalBase):
+
+    terminal_prompts_re = [
+        re.compile(r'[\r\n]?[a-zA-Z]{1}[a-zA-Z0-9-]*[>|#|%](?:\s*)$'),
+        re.compile(r'[\r\n]?[a-zA-Z]{1}[a-zA-Z0-9-]*\(.+\)#(?:\s*)$')
+    ]
+
+    terminal_errors_re = [
+        re.compile(r"% ?Error"),
+        re.compile(r"^% \w+", re.M),
+        re.compile(r"% ?Bad secret"),
+        re.compile(r"invalid input", re.I),
+        re.compile(r"(?:incomplete|ambiguous) command", re.I),
+        re.compile(r"connection timed out", re.I),
+        re.compile(r"[^\r\n]+ not found", re.I),
+        re.compile(r"'[^']' +returned error code: ?\d+"),
+        re.compile(r"syntax error"),
+        re.compile(r"unknown command"),
+        re.compile(r"user not present")
+    ]
+
+    def on_open_shell(self):
+        try:
+            self._exec_cli_command('terminal length 0')
+        except AnsibleConnectionFailure:
+            raise AnsibleConnectionFailure('unable to set terminal parameters')
+
+
+