slaprunner: prevents overwrite of the current software released

if the user has changed the pre-installed one

software/slaprunner/instance-runner.cfg

@@ -501,7 +501,8 @@ stop-on-error = true
 reference = $${slap-parameter:slapos-reference}
 location = $${slapos-repo:location}
 environment = export PATH=${git:location}/bin:$PATH;
-command = $${:environment} (cd $${:location} && git checkout $${:reference} && SR=$${slap-parameter:slapos-software} && if [ -n "$SR" ]; then echo workspace/slapos/$${slap-parameter:slapos-software}/ > $${directory:etc}/.project; fi) 
+command = $${:environment} (cd $${:location} && git checkout $${:reference} && echo "$${directory:etc}/.project" && SR=$${slap-parameter:slapos-software} && if [ -n "$SR" ] && [ ! -f "$${directory:etc}/.project" ]; then echo workspace/slapos/$${slap-parameter:slapos-software}/ > $${directory:etc}/.project; fi) 
+update-command = $${:command}
 
 [prepare-software]
 recipe = slapos.cookbook:wrapper