Skip multiple servers testbed parsing on branch 202405 (#458)

In PRs: sonic-net/sonic-mgmt#15643 and
sonic-net/sonic-mgmt#15881
We implemented multi-servers testbed design, however, to enable parsing
multi-servers testbed definition, raise this PR to fix out of key error.
The code is already in master branch, and we only need the four lines
code to be backport to 202411 and 202405

Author: w1nda

ansible/library/test_facts.py

@@ -169,10 +169,10 @@ def _read_testbed_topo_from_yaml():
             with open(self.testbed_filename) as f:
                 tb_info = yaml.safe_load(f)
                 for tb in tb_info:
-                    if tb["ptf_ip"]:
+                    if "ptf_ip" in tb and tb["ptf_ip"]:
                         tb["ptf_ip"], tb["ptf_netmask"] = \
                             _cidr_to_ip_mask(tb["ptf_ip"])
-                    if tb["ptf_ipv6"]:
+                    if "ptf_ipv6" in tb and tb["ptf_ipv6"]:
                         tb["ptf_ipv6"], tb["ptf_netmask_v6"] = \
                             _cidr_to_ip_mask(tb["ptf_ipv6"])
                     tb["duts"] = tb.pop("dut")

tests/common/testbed.py

@@ -107,10 +107,10 @@ def _read_testbed_topo_from_yaml(self):
         with open(self.testbed_filename) as f:
             tb_info = yaml.safe_load(f)
             for tb in tb_info:
-                if tb["ptf_ip"]:
+                if "ptf_ip" in tb and tb["ptf_ip"]:
                     tb["ptf_ip"], tb["ptf_netmask"] = \
                         self._cidr_to_ip_mask(tb["ptf_ip"])
-                if tb["ptf_ipv6"]:
+                if "ptf_ipv6" in tb and tb["ptf_ipv6"]:
                     tb["ptf_ipv6"], tb["ptf_netmask_v6"] = \
                         self._cidr_to_ip_mask(tb["ptf_ipv6"])
                 tb["duts"] = tb.pop("dut")