internal/trace/v2: tolerate having a P in GoCreateSyscall
On non-pthread platforms, it's totally possible for the same M to
GoCreateSyscall/GoDestroySyscall on the same thread multiple times. That
same thread may hold onto its P through all those calls.
For #64060.
Change-Id: Ib968bfd439ecd5bc24fc98d78c06145b0d4b7802
Reviewed-on: https://go-review.googlesource.com/c/go/+/545515 Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>