During plugin init the default firewall section is created.
If it already exists, it will be updated, which causes race condition
in case of multiple controllers.
There is no need to update the default section during init, unless the
nsx.ini configuration changed, in which case admin utility should be used
to update the section: nsxadmin -r firewall-sections -o nsx-update
In addition, catch exceptions when creating the section, as there also might
be a race condition there.
Change-Id: I19b238a561af95e856d9dae32764ce4d484df767
f9aa6bd805