ceph-disk: --verbose shows a stack trace on error

When running with --verbose, do not hide the stack trace from the user
when an exception is raised. It is most helpful to figure out when the
exception actually happened.

Signed-off-by: Loic Dachary <ldachary@redhat.com>

src/ceph-disk

@@ -3175,8 +3175,15 @@ def main():
     setup_statedir(args.statedir)
     setup_sysconfdir(args.sysconfdir)
 
-    try:
+    if args.verbose:
         args.func(args)
+    else:
+        main_catch(args.func, args)
+
+def main_catch(func, args):
+
+    try:
+        func(args)
 
     except Error as e:
         raise SystemExit(