dgr try: when instantiating the aci-manifest.yml template, the values in /attributes are not used

[PaulGrandperrin]

Excerpt of failure log:

16:16:00 FATAL  d/aci-builder/bin-run/main.go:27  Build failed                                
                       d/a/bin-run/builder.go:117 Failed to process manifest template          aci=aci-nginx-extras content=---
name: aci.blbl.cr/aci-nginx-extras:{{.nginx_version}}-0
aci:
  app:
    exec: [ "/bin/bash" ]
  dependencies:
    - aci.blbl.cr/aci-debian:9.4-8
    - aci.blbl.cr/aci-common:7
builder:
  dependencies:
   - aci.blbl.cr/aci-debian:9.4-8
               dgr/dgr/common/dgr-manifest.go:149 Templating result of manifest have <no value> line=2 source=---
name: aci.blbl.cr/aci-nginx-extras:{{.nginx_version}}-0
aci:
  app:
    exec: [ "/bin/bash" ]
  dependencies:
    - aci.blbl.cr/aci-debian:9.4-8
    - aci.blbl.cr/aci-common:7
builder:
  dependencies:
   - aci.blbl.cr/aci-debian:9.4-8 text=name: aci.blbl.cr/aci-nginx-extras:<no value>-0
16:16:00 FATAL             dgr/dgr/command.go:155 Try command failed                          
                         dgr/dgr/aci-build.go:75  Builder container return with failed status  aci=aci.blbl.cr/aci-nginx-extras
                 dgr/dgr/common/rkt-client.go:261 Run failed                                   config={Path: InsecureOptions:[ondisk image] dir: LocalConfig: SystemConfig: UserConfig: PullPolicy: TrustKeysFromHttps:false NoStore:false StoreOnly:false}
                                                  exit status 1