Don't show backtrace when metrics script times out

Rescue Exception instead of default StandardError when running cartridge
and application metrics scripts because the timeout exception generated
by oo_spawn (ShellExecutionException) currently extends Exception, so
rescue => e won't catch these errors.

Write errors to stdout instead of stderr so they can be displayed in the
logs.

This commit fixes bug 1086549.
Merge pull request #5239 from ncdc/bug/1086549

Merged by openshift-bot