net/http: bgErr is unused; remove it
net/http: bgErr is unused; remove it

Fixes #20196.

Change-Id: Ib87f6e9e27a38f21f860b7150c818d77be653dd3
Reviewed-on: https://go-review.googlesource.com/42370
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

akutz/go,ImJasonH/go,CAFxX/go,Cofyc/go,polyverse-security/go,polyverse-security/go,golang/go,codestation/go,akutz/go,CAFxX/go,golang/go,nawawi/go,golang/go,vsekhar/elastic-go,derekmarcotte/go,akutz/go,golang/go,ImJasonH/go,cloudflare/go,derekmarcotte/go,akutz/go,cloudflare/go,vsekhar/elastic-go,codestation/go,nawawi/go,Cofyc/go,Cofyc/go,josharian/go,Cofyc/go,nawawi/go,Cofyc/go,christopher-henderson/Go,Cofyc/go,ImJasonH/go,cloudflare/go,CAFxX/go,codestation/go,cloudflare/go,vsekhar/elastic-go,josharian/go,cloudflare/go,josharian/go,nawawi/go,polyverse-security/go,golang/go,akutz/go,polyverse-security/go,CAFxX/go,akutz/go,nawawi/go,CAFxX/go,cloudflare/go,golang/go,akutz/go,josharian/go,derekmarcotte/go,nawawi/go,josharian/go,codestation/go,akutz/go,josharian/go,vsekhar/elastic-go,derekmarcotte/go,CAFxX/go,golang/go,polyverse-security/go,josharian/go,derekmarcotte/go,vsekhar/elastic-go,ImJasonH/go,CAFxX/go,cloudflare/go,ImJasonH/go,polyverse-security/go,derekmarcotte/go,vsekhar/elastic-go,CAFxX/go,josharian/go,Cofyc/go,polyverse-security/go,ImJasonH/go,ImJasonH/go,nawawi/go,codestation/go,golang/go,Cofyc/go,cloudflare/go,polyverse-security/go,vsekhar/elastic-go,vsekhar/elastic-go,derekmarcotte/go,nawawi/go,codestation/go,derekmarcotte/go,codestation/go,codestation/go,ImJasonH/go