fix(cloudstack): avoid UnboundLocalError for primary_nic on NoDHCPLeaseError

[sundeep8967]

Problem

In DataSourceCloudStack._get_data, when self.perform_dhcp_setup is False, primary_nic is never assigned. If get_vr_address(self.distro) subsequently raises a NoDHCPLeaseError, the exception handler attempts to log:

LOG.warning("Unable to obtain a DHCP lease on %s", primary_nic)

which crashes with:

UnboundLocalError: cannot access local variable 'primary_nic' where it is not associated with a value

Solution

• Initialized primary_nic = None before the DHCP setup branch in DataSourceCloudStack._get_data.
• Added unit test test_get_data_no_dhcp_lease_error_without_dhcp_setup under tests/unittests/sources/test_cloudstack.py to verify that NoDHCPLeaseError with perform_dhcp_setup=False logs cleanly and returns False without raising an UnboundLocalError.

Fixes #6838

Testing

• Verified test failure prior to the fix (UnboundLocalError reproduced).
• Verified that all 29 tests in tests/unittests/sources/test_cloudstack.py pass with 100% success after the fix.