NetworkManagementService: adjust the qtaguid idx to new kernel

https://partner.source.android.com/g/#/c/8968/ introduced

  idx iface acct_tag_hex uid_tag_int cnt_set ...
  2 wlan0 0x0 10022 0 ...
  3 wlan0 0x0 10022 1 ...
  4 wlan0 0x3010000000000000 10022 0 ...
  5 wlan0 0x3010000000000000 10022 1 ...

so treat it as monotonic starting a idx 1 for header line.

Change-Id: Ie1d0ec9a0b7103620a93b0ef0b01c13fe4162616