net/http: deflake TestClientTimeout
net/http: deflake TestClientTimeout

This test was only enabled by default today so it hasn't been hardened
by build.golang.org. Welcome to the ring, TestClientTimeout.

Change-Id: I1967f6c825699f13f6c659dc14d3c3c22b965272
Reviewed-on: https://go-review.googlesource.com/33101
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

Cofyc/go,goodlang/good,cloudflare/go,akutz/go,suncycheng/go,josharian/go,polyverse-security/go,derekmarcotte/go,akutz/go,linux-on-ibm-z/go,cloudflare/go,CAFxX/go,golang/go,CAFxX/go,linux-on-ibm-z/go,cloudflare/go,CAFxX/go,Cofyc/go,josharian/go,akutz/go,goodlang/good,cloudflare/go,goodlang/good,suncycheng/go,codestation/go,CAFxX/go,linux-on-ibm-z/go,CAFxX/go,derekmarcotte/go,golang/go,derekmarcotte/go,ImJasonH/go,ImJasonH/go,linux-on-ibm-z/go,codestation/go,goodlang/good,ImJasonH/go,Cofyc/go,goodlang/good,josharian/go,codestation/go,vsekhar/elastic-go,Cofyc/go,Cofyc/go,ImJasonH/go,nawawi/go,CAFxX/go,vsekhar/elastic-go,vsekhar/elastic-go,suncycheng/go,suncycheng/go,josharian/go,polyverse-security/go,vsekhar/elastic-go,ImJasonH/go,codestation/go,akutz/go,CAFxX/go,nawawi/go,christopher-henderson/Go,nawawi/go,cloudflare/go,polyverse-security/go,codestation/go,cloudflare/go,vsekhar/elastic-go,josharian/go,akutz/go,linux-on-ibm-z/go,derekmarcotte/go,josharian/go,polyverse-security/go,golang/go,vsekhar/elastic-go,linux-on-ibm-z/go,suncycheng/go,codestation/go,golang/go,derekmarcotte/go,cloudflare/go,nawawi/go,akutz/go,polyverse-security/go,codestation/go,nawawi/go,ImJasonH/go,vsekhar/elastic-go,golang/go,polyverse-security/go,akutz/go,polyverse-security/go,derekmarcotte/go,suncycheng/go,derekmarcotte/go,golang/go,goodlang/good,goodlang/good,goodlang/good,josharian/go,Cofyc/go,linux-on-ibm-z/go,vsekhar/elastic-go,nawawi/go,cloudflare/go,CAFxX/go,akutz/go,nawawi/go,linux-on-ibm-z/go,derekmarcotte/go,ImJasonH/go,Cofyc/go,josharian/go,suncycheng/go,Cofyc/go,polyverse-security/go,codestation/go,golang/go,suncycheng/go,nawawi/go,golang/go,ImJasonH/go