os: skip TestPipeThreads on Solaris
os: skip TestPipeThreads on Solaris

I don't know why it is not working.  Filed issue 19111 for this.

Fixes build.

Update #19111.

Change-Id: I76f8d6aafba5951da2f3ad7d10960419cca7dd1f
Reviewed-on: https://go-review.googlesource.com/37092
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

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