Potential NPE dereference fix

Signed-off-by: Laszlo Hornyak <laszlo.hornyak@gmail.com>
new testcase for AccountManagerImpl.deleteUserAccount

Signed-off-by: Laszlo Hornyak <laszlo.hornyak@gmail.com>
Return isolation methods as a part of listPhysicalNetworks call
Revert "Return isolation methods as a part of listPhysicalNetworks call"

This reverts commit 316f23ed5fe7ae77e1054add368b2c05dfeef331.
CLOUDSTACK-6478: Failed to download Template when having 3 SSVM's in one
zone on Vmware.