selftests: forwarding: Make vxlan-bridge-1d pass on debug kernels

selftests: forwarding: Make vxlan-bridge-1d pass on debug kernels

The ageing time used by the test is too short for debug kernels and
results in entries being aged out prematurely [1].

Fix by increasing the ageing time.

The same change was done for the VLAN-aware version of the test in
commit dfbab74044be ("selftests: forwarding: Make vxlan-bridge-1q pass
on debug kernels").

[1]
 # ./vxlan_bridge_1d.sh
 [...]
 # TEST: VXLAN: flood before learning                              [ OK ]
 # TEST: VXLAN: show learned FDB entry                             [ OK ]
 # TEST: VXLAN: learned FDB entry                                  [FAIL]
 # veth3: Expected to capture 0 packets, got 4.
 # RTNETLINK answers: No such file or directory
 # TEST: VXLAN: deletion of learned FDB entry                      [ OK ]
 # TEST: VXLAN: Ageing of learned FDB entry                        [FAIL]
 # veth3: Expected to capture 0 packets, got 2.
 [...]

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240707095458.2870260-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>