Non-SNAPSHOT Marketplace package install should not force other packages upgrade to SNAPSHOT version

From Nuxeo 5.8 CAP

1. I install Nuxeo Signature 2.0.

   ./nuxeoctl mp-install nuxeo-signature-2.0.0
   Detected Tomcat server.
   Nuxeo home:          /Applications/nuxeo-cap-5.8-tomcat 2
   Nuxeo configuration: /Applications/nuxeo-cap-5.8-tomcat 2/bin/nuxeo.conf
   Include template: /Applications/nuxeo-cap-5.8-tomcat 2/templates/common-base
   Include template: /Applications/nuxeo-cap-5.8-tomcat 2/templates/common
   Include template: /Applications/nuxeo-cap-5.8-tomcat 2/templates/default
   
   Dependency resolution:
     Installation order: nuxeo-signature-2.0.0
   

   Here is the list of packages I have:

   ./nuxeoctl mp-list
   Detected Tomcat server.
   Nuxeo home:          /Applications/nuxeo-cap-5.8-tomcat 2
   Nuxeo configuration: /Applications/nuxeo-cap-5.8-tomcat 2/bin/nuxeo.conf
   Include template: /Applications/nuxeo-cap-5.8-tomcat 2/templates/common-base
   Include template: /Applications/nuxeo-cap-5.8-tomcat 2/templates/common
   Include template: /Applications/nuxeo-cap-5.8-tomcat 2/templates/default
   Local packages:
    addon  downloaded	nuxeo-dam (id: nuxeo-dam-5.8.0)
    addon  downloaded	nuxeo-dm (id: nuxeo-dm-5.8.0)
    addon  downloaded	nuxeo-rest-api (id: nuxeo-rest-api-5.8.0)
    addon     started	nuxeo-signature (id: nuxeo-signature-2.0.0)
    addon  downloaded	nuxeo-social-collaboration (id: nuxeo-social-collaboration-5.8.0)
   

2. I install Nuxeo DM, which is actually needed by Signature.

   ./nuxeoctl mp-install nuxeo-dm
   Detected Tomcat server.
   Nuxeo home:          /Applications/nuxeo-cap-5.8-tomcat 2
   Nuxeo configuration: /Applications/nuxeo-cap-5.8-tomcat 2/bin/nuxeo.conf
   Include template: /Applications/nuxeo-cap-5.8-tomcat 2/templates/common-base
   Include template: /Applications/nuxeo-cap-5.8-tomcat 2/templates/common
   Include template: /Applications/nuxeo-cap-5.8-tomcat 2/templates/default
   
   Dependency resolution:
     Installation order: nuxeo-dm-5.8.0/nuxeo-signature-2.1.0-SNAPSHOT
     Packages to upgrade: nuxeo-signature:2.0.0
   
   Do you want to continue (yes/no)? [yes] 
   

   => the system tries to upgrade Singature to a SNAPSHOT version.