deploy: Add status module

This is used to keep track of the deployment status. The status file
is kept under the 'state' dir. The check() method is used to find
conflicting components or the ones that have already been installed.
The update() method adds an entry in the node's section. If in dry-run
this file is not written back to permanent storage (kept in memory).
Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>

snf-deploy/snfdeploy/status.py

+# Copyright (C) 2010-2014 GRNET S.A.
+#
+# This program 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.
+#
+# This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import ConfigParser
+import os
+import sys
+from snfdeploy import constants
+from snfdeploy import config
+
+status = sys.modules[__name__]
+
+
+def check(ip, component_class):
+    try:
+        return status.cfg.get(ip, component_class.__name__, True)
+    except (ConfigParser.NoSectionError, ConfigParser.NoOptionError):
+        return None
+
+
+def update(ip, component_class, stat):
+    if not status.cfg.has_section(ip):
+        status.cfg.add_section(ip)
+    status.cfg.set(ip, component_class.__name__, stat)
+
+
+def write():
+    with open(status.statusfile, 'wb') as configfile:
+        status.cfg.write(configfile)
+
+
+def init():
+    status.state_dir = config.state_dir
+    status.cfg = ConfigParser.ConfigParser()
+    status.cfg.optionxform = str
+    status.statusfile = os.path.join(config.state_dir, constants.STATUS_FILE)
+    status.cfg.read(status.statusfile)