Fix TLS from environment variables in client
Fix TLS from environment variables in client

A recent change accidently caused any TLS configuration in FromEnv to be
ignored. This change alters WithHost to create a new http client only if
one doesn't already exist, and otherwise applies the logic to the
transport on the existing client. This preserves the TLS configuration
that might already be on the client.

Signed-off-by: Drew Erny <83d780db39fae693cf18623ace93c7ec0dc91590@docker.com>

jlhawn/docker,tophj-ibm/moby,moul/docker,jameszhan/docker,x1022as/docker,tophj-ibm/moby,bearstech/moby,bearstech/moby,unclejack/docker,ibuildthecloud/docker,yosifkit/docker,Ramzec/docker,tmp6154/docker,konstruktoid/docker-1,scotttlin/docker,nawawi/docker,AkihiroSuda/docker,ibuildthecloud/docker,konstruktoid/docker-upstream,justincormack/docker,maxamillion/docker,konstruktoid/docker-upstream,x1022as/docker,jameszhan/docker,mikebrow/docker,kolyshkin/moby,laijs/moby,pradipd/moby,maxamillion/docker,mahak/docker,tophj-ibm/moby,docker/docker,nawawi/docker,vdemeester/docker,estesp/docker,scotttlin/docker,dims/docker,yongtang/docker,tmp6154/docker,tophj-ibm/docker,tonistiigi/docker,dims/docker,allencloud/docker,crosbymichael/docker,unclejack/docker,moby/moby,docker/docker,scotttlin/docker,moul/docker,jlhawn/docker,KingEmet/docker,nawawi/docker,konstruktoid/docker-upstream,nalind/docker,djs55/docker,dmcgowan/docker,SvenDowideit/docker,justincormack/docker,gnailuy/docker,SvenDowideit/docker,noironetworks/docker,laijs/docker,pradipd/moby,mikebrow/docker,johnstep/moby-moby,trebonian/docker,Ramzec/docker,rancher/docker,KarthikNayak/docker,jameszhan/docker,docker/docker,AkihiroSuda/docker,nalind/docker,tophj-ibm/docker,tmp6154/docker,noironetworks/docker,Ramzec/docker,flavio/docker,AkihiroSuda/docker,kojiromike/docker,YuPengZTE/docker,moby/moby,noironetworks/docker,Ramzec/docker,Mokolea/docker,moul/docker,tonistiigi/docker,laijs/moby,bearstech/moby,cpuguy83/docker,kolyshkin/docker,jvanz/docker,djs55/docker,allencloud/docker,Mokolea/docker,vdemeester/docker,jwhonce/docker,dmcgowan/docker,rremer/moby,dccurtis/docker,jwhonce/docker,moul/docker,Mokolea/docker,thaJeztah/docker,trebonian/docker,kolyshkin/moby,gnailuy/docker,jimjag/docker,KingEmet/docker,bearstech/moby,jimjag/docker,duglin/docker,gnailuy/docker,nalind/docker,ibuildthecloud/docker,paralin/docker,tophj-ibm/docker,jvanz/docker,yongtang/docker,yosifkit/docker,vdemeester/docker,rancher/docker,crosbymichael/docker,YuPengZTE/docker,yongtang/docker,djs55/docker,kolyshkin/docker,trebonian/docker,jthelin/docker,kolyshkin/moby,paralin/docker,moby/moby,YuPengZTE/docker,dccurtis/docker,paralin/docker,estesp/docker,dmcgowan/docker,dccurtis/docker,estesp/docker,pradipd/moby,laijs/docker,jvanz/docker,cpuguy83/docker,jwhonce/docker,justincormack/docker,Mokolea/docker,trebonian/docker,yosifkit/docker,jimjag/docker,rremer/moby,jimjag/docker,x1022as/docker,rremer/moby,konstruktoid/docker-1,jthelin/docker,unclejack/docker,paralin/docker,duglin/docker,ibuildthecloud/docker,dims/docker,ibuildthecloud/docker,flavio/docker,cpuguy83/docker,yosifkit/docker,thaJeztah/docker,flavio/docker,johnstep/moby-moby,duglin/docker,mikebrow/docker,laijs/docker,mahak/docker,moby/moby,konstruktoid/docker-upstream,kojiromike/docker,laijs/moby,crosbymichael/docker,allencloud/docker,gnailuy/docker,KarthikNayak/docker,thaJeztah/docker,thaJeztah/docker,johnstep/moby-moby,maxamillion/docker,mahak/docker,jlhawn/docker,SvenDowideit/docker,flavio/docker,tonistiigi/docker,KarthikNayak/docker,cpuguy83/docker,mahak/docker,konstruktoid/docker-1,nalind/docker,kojiromike/docker,nawawi/docker,KingEmet/docker,rancher/docker,AkihiroSuda/docker