runtime: fix GODEBUG=schedtrace=X delay handling.
runtime: fix GODEBUG=schedtrace=X delay handling.

debug.schedtrace is an int32. Convert it to int64 before
multiplying with constant 1000000. Otherwise, schedtrace
values more than 2147 result in int32 overflow causing
incorrect delays between traces.

Change-Id: I064e8d7b432c1e892a705ee1f31a2e8cdd2c3ea3
Reviewed-on: https://go-review.googlesource.com/17712
Reviewed-by: Austin Clements <7ea35d812706d9213868749011af1ed4fa2f6aa0@google.com>
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

derekmarcotte/go,cloudflare/go,Endika/go,Samurais/go,vanloswang/go,codestation/go,CAFxX/go,miolini/go,mwhudson/go,sndnvaps/go,cloudflare/go,mwhudson/go,codestation/go,kim-racktop/go,cloudflare/go,theif519/go,miolini/go,suncycheng/go,codestation/go,codestation/go,akutz/go,suncycheng/go,goodlang/good,Cofyc/go,kim-racktop/go,4ad/go,momchil-velikov/go,vsekhar/elastic-go,derekmarcotte/go,golang/go,suncycheng/go,vsekhar/elastic-go,momchil-velikov/go,Cofyc/go,derekmarcotte/go,vanloswang/go,deft-code/go,goodlang/good,josharian/go,4ad/go,Cofyc/go,akutz/go,4ad/go,vsekhar/elastic-go,deft-code/go,Samurais/go,polyverse-security/go,vanloswang/go,ganboing/go-esx,akutz/go,roth1002/go,roth1002/go,ImJasonH/go,cyberroadie/go,ganboing/go-esx,golang/go,CAFxX/go,nawawi/go,binarycrusader/go,polyverse-security/go,theif519/go,cloudflare/go,4ad/go,cloudflare/go,Samurais/go,ImJasonH/go,nawawi/go,linux-on-ibm-z/go,nawawi/go,linux-on-ibm-z/go,momchil-velikov/go,cyberroadie/go,nawawi/go,derekmarcotte/go,momchil-velikov/go,mwhudson/go,josharian/go,ImJasonH/go,golang/go,vsekhar/elastic-go,CAFxX/go,binarycrusader/go,theif519/go,miolini/go,binarycrusader/go,vanloswang/go,nawawi/go,sndnvaps/go,Samurais/go,vsekhar/elastic-go,4ad/go,derekmarcotte/go,vsekhar/elastic-go,Cofyc/go,cyberroadie/go,vanloswang/go,josharian/go,derekmarcotte/go,cyberroadie/go,suncycheng/go,roth1002/go,linux-on-ibm-z/go,mwhudson/go,ImJasonH/go,sndnvaps/go,sndnvaps/go,binarycrusader/go,ImJasonH/go,miolini/go,momchil-velikov/go,cloudflare/go,akutz/go,codestation/go,Endika/go,josharian/go,cyberroadie/go,akutz/go,suncycheng/go,linux-on-ibm-z/go,4ad/go,derekmarcotte/go,Samurais/go,linux-on-ibm-z/go,cyberroadie/go,vanloswang/go,cloudflare/go,sndnvaps/go,linux-on-ibm-z/go,sndnvaps/go,cyberroadie/go,ganboing/go-esx,suncycheng/go,binarycrusader/go,roth1002/go,josharian/go,deft-code/go,momchil-velikov/go,CAFxX/go,golang/go,polyverse-security/go,josharian/go,polyverse-security/go,miolini/go,kim-racktop/go,CAFxX/go,Samurais/go,Cofyc/go,ganboing/go-esx,ImJasonH/go,Cofyc/go,theif519/go,linux-on-ibm-z/go,cyberroadie/go,Endika/go,Endika/go,Samurais/go,ganboing/go-esx,binarycrusader/go,vsekhar/elastic-go,codestation/go,polyverse-security/go,deft-code/go,akutz/go,mwhudson/go,josharian/go,theif519/go,sndnvaps/go,sndnvaps/go,golang/go,goodlang/good,mwhudson/go,goodlang/good,ImJasonH/go,CAFxX/go,deft-code/go,golang/go,mwhudson/go,kim-racktop/go,deft-code/go,goodlang/good,Cofyc/go,golang/go,ImJasonH/go,ganboing/go-esx,binarycrusader/go,Endika/go,momchil-velikov/go,kim-racktop/go,deft-code/go,theif519/go,kim-racktop/go,ganboing/go-esx,golang/go,ganboing/go-esx,4ad/go,roth1002/go,miolini/go,goodlang/good,suncycheng/go,polyverse-security/go,nawawi/go,codestation/go,christopher-henderson/Go,vanloswang/go,nawawi/go,akutz/go,Samurais/go,CAFxX/go,goodlang/good,derekmarcotte/go,roth1002/go,deft-code/go,binarycrusader/go,akutz/go,miolini/go,theif519/go,miolini/go,polyverse-security/go,kim-racktop/go,kim-racktop/go,vanloswang/go,cloudflare/go,Endika/go,goodlang/good,theif519/go,roth1002/go,Endika/go,CAFxX/go,momchil-velikov/go,nawawi/go,4ad/go,roth1002/go,linux-on-ibm-z/go,josharian/go,Endika/go,vsekhar/elastic-go,mwhudson/go,codestation/go,Cofyc/go,suncycheng/go,polyverse-security/go