fix(tests): Adjust skeleton test timeouts to reduce flakyness

[dangome3]

Increase the curl event checker time limit from 30 to 60 seconds and change the curl container imagePullPolicy from Always to IfNotPresent.

Tested several times:

--- PASS: TestSkeletonBasic (15.05s)
    --- PASS: TestSkeletonBasic/Get_Minimum_Kernel_Version (0.00s)
        --- PASS: TestSkeletonBasic/Get_Minimum_Kernel_Version/Lookup_Kernel_Version (0.00s)
    --- PASS: TestSkeletonBasic/Run_Event_Checks (2.98s)
        --- PASS: TestSkeletonBasic/Run_Event_Checks/Run_Event_Checks (2.98s)
    --- PASS: TestSkeletonBasic/Run_Workload (15.05s)
        --- PASS: TestSkeletonBasic/Run_Workload/Wait_for_Checker (0.00s)
        --- PASS: TestSkeletonBasic/Run_Workload/Run_Workload (10.02s)
        --- PASS: TestSkeletonBasic/Run_Workload/Run_Metrics_Checks (0.02s)
        --- PASS: TestSkeletonBasic/Run_Workload/Uninstall_policy (5.01s)

Issue related: https://github.com/isovalent/hubble-fgs/issues/6518 Found several pipelines failing due to timeout issue so I increased them. The execution time should not be affected when the network is working properly, the current change just add additional changes to make the tests work

[FedeDP]

Tested several times:

Question: were you able to reproduce the issue before your changes?

[dangome3]

Tested several times:

Question: were you able to reproduce the issue before your changes?

There are some pipelines that failed