xenserver: Collect xenserver configured timezone in bugtool report

xenserver: Collect xenserver configured timezone in bugtool report

xenserver logs can be in any timezone, as configured by user
during install time. Also, the timezone data is not currently
recorded in the bugtool report. Therefore, it is currently not
possible to easily correlate logs collected on xenserver with
logs from other devices on the network.

With this change, system-configuration capability of the bugtool plugin
has been added. Also, added an extension to this capability to collect
the time information in RFC3339 format, which includes the system timezone.

Signed-off-by: Sajjad Lateef <slateef@nicira.com>