MFC r211396 (originally committed by andre):

MFC r211396 (originally committed by andre):

Add uma_zone_get_max() to obtain the effective limit after a call
to uma_zone_set_max().

The UMA zone limit is not exactly set to the value supplied but rounded up to
completely fill the backing store increment (a page normally).  This can lead to
surprising situations where the number of elements allocated from UMA is higher
than the supplied limit value.  The new get function reads back the effective
value so that the supplied limit value can be adjusted to the real limit.

Reviewed by:	jeffr

git-svn-id: svn://svn.freebsd.org/base/stable/8@214861 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f