Logcat text: small fixes

  * fix exporting "beginning of" frame logs into info field
  * add missing "Failure" level to regexp in wiretap part
  * remove usage of GDateTime from wiretap part

Change-Id: Ibdea730623241cccbbc1694a34daa308e48c0a89
Reviewed-on: https://code.wireshark.org/review/3493
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>