Systems with lots of geom providers can end up with a kern.geom.confxml
value too large for the buffer allocated. Work around this by retrying
a few times with larger buffer sizes.

Submitted by:	Scott Ferris <scott.ferris@isilon.com>
Reviewed by:	mlaier, ngie
Sponsored by:	EMC Isilon Storage Division


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271085 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f