probe: Fix printing goal limits in list-mounts command

This commit fixes an issue introduced in one of the previous commits
which makes lizardfs-probe unable to print values of default goal limits
(which are now 1-20), because these numbers don't fulfill the condition:

  mount.maxGoal >= 1 && mount.maxGoal <= 9

The test test_probe_list_mounts also needed to be changed to reflect
the change in the default values.

Change-Id: Id3c29b83144c925c1e4cc2e3575239d0161339b7