Management update

Update to latest mgmt.git:

* mgmt 76f0e7e...97be48e (5):
  > md5sum: fix ugly spew when file doesn't exist
  > ls: handle non-existing files correctly
  > mgmt/crash: Fix printf format string in test.groovy
  > mgmt: Kill obsolete Rhino-based CLI code
  > mgmt/perf: Fix "perf callstack" usability gitch if there are no traces

The important part is Rhino-based CLI removal which seem to cause lot of
problems for people building OSv on other distributions. The usability
fixes to perf, ls, and md5sum commands are also worth the update.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>