ovs-bugtool: Added --ovs option to get only ovs related information

ovs-bugtool: Added --ovs option to get only ovs related information

Option --ovs is added for ovs-bugtool command to collect
only OpenvSwitch relevant information. To perform
filtering in plugins, a new xml attribute filters="ovs" (optional)
would be required in element 'command','files','directory' in
openvswitch.xml. Value of 'filters' attribute will be compared
with filtering option in load_plugins to get all relevant operation
to collect information. If no "--ovs" option is passed then it will
behave as earlier.

Fixed an issue which occurs in scenario where option '--yestoall'
is not passed and user keeps entering "y" or "n" on prompt.

Plus, trailing whitespaces are fixed. White space before '=' and
after in function def and call is also fixed.

Signed-off-by: Arun Sharma <arun.sharma@calsoftinc.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>