Fix check for juju-run path

Author: bcoles

modules/exploits/linux/local/juju_run_agent_priv_esc.rb

@@ -55,14 +55,14 @@ def initialize(info = {})
   def check
     juju_run_path = cmd_exec 'which juju-run'
 
-    if juju_run_path.blank?
-      vprint_error 'juju-run is NOT installed'
-      return CheckCode::Safe
+    if juju_run_path.start_with? '/'
+      vprint_good 'juju-run is installed'
+      return CheckCode::Detected
     end
 
-    vprint_good 'juju-run is installed'
+    vprint_error 'juju-run is NOT installed'
 
-    CheckCode::Detected
+    CheckCode::Safe
   end
 
   def unit_names