Merge pull request #1842 from teojgo/bugfix/containers_stagedir

[bugfix] Fix passing of stagedir to container platforms

Author: Vasileios Karakasis

reframe/core/pipeline.py

@@ -1293,9 +1293,11 @@ def run(self):
             self.container_platform.validate()
 
             # We replace executable and executable_opts in case of containers
-            self.executable = self.container_platform.launch_command()
+            self.executable = self.container_platform.launch_command(
+                self.stagedir)
             self.executable_opts = []
-            prepare_container = self.container_platform.emit_prepare_commands()
+            prepare_container = self.container_platform.emit_prepare_commands(
+                self.stagedir)
             if prepare_container:
                 self.prerun_cmds += prepare_container