tpm_device.py: clean audit before vm start

[yanqzhan]

Cleaning audit logs should be before vm start, and need clean all
audit.log*(.1, .2, etc) files. Also move it later to wait more time.
And replace ausearch cmd since it can not capture well sometimes,
audit.log can reflect actual info instead.

[yanqzhan]

(1/1) type_specific.io-github-autotest-libvirt.virtual_devices.tpm_device.normal_test.tpm-crb_model.external.start_vm: PASS (30.38 s)

[yanqzhan]

Before:(only reproduces online in jenkins)
Command 'ausearch -m VIRT_RESOURCE| grep 'tpm-external'' failed.\nstdout: b''\nstderr: b'<no matches>\n'\nadditional_info: None (12.60 s)
After:
Check fix history in $jenkins/job/libvirt-RHEL-9.4-runtest-x86_64-function-tpm_emulator/44/testReport/rhel/virtual_devices/tpm_device_normal_test_tpm_crb_model_external_start_vm/history/

2024-09-26 08:51:21,525 avocado.utils.process process          L0657 INFO | Running 'truncate -s 0  /var/log/audit/audit.log*'
2024-09-26 08:51:23,063 avocado.utils.process process          L0714 INFO | Command 'truncate -s 0  /var/log/audit/audit.log*' finished with 0 after 1.536528244s
2024-09-26 08:51:23,063 avocado.utils.process process          L0657 INFO | Running 'cat /var/log/audit/audit.log| grep 'tpm-external''
2024-09-26 08:51:23,066 avocado.utils.process process          L0714 INFO | Command 'cat /var/log/audit/audit.log| grep 'tpm-external'' finished with 1 after 0.001594883s
2024-09-26 08:51:23,078 avocado.virttest.libvirt_vm libvirt_vm       L2653 DEBUG| Starting vm 'avocado-vt-vm1'
---------
2024-09-26 08:51:23,613 avocado.utils.process process          L0657 INFO | Running 'cat /var/log/audit/audit.log| grep 'tpm-external''
2024-09-26 08:51:23,616 avocado.utils.process process          L0473 DEBUG| [stdout] type=VIRT_RESOURCE msg=audit(1727355083.438:13226): pid=137870 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:virtd_t:s0-s0:c0.c1023 msg='virt=kvm resrc=tpm-external reason=start vm="avocado-vt-vm1" uuid=0fe66337-90de-47ab-b265-64fa0196f14c device="/var/tmp/guest-swtpm.sock" exe="/usr/sbin/virtqemud" hostname=? addr=? terminal=? res=success'UID="root" AUID="unset"

[yanqzhan]

@chunfuwen This is minor fix for jira LIBVIRTAT-19404. Please help review. Thanks.