Accept udev and dracut paths specified by ./configure

There are two common locations where udev and dracut components are
commonly installed.  When building packages using the 'make rpm|deb'
targets check those common locations and pass them to rpmbuild.  For
non-standard configurations these values can be provided by the
the following configure options:

  --with-udevdir=DIR      install udev helpers [default=check]
  --with-udevruledir=DIR  install udev rules [[UDEVDIR/rules.d]]
  --with-dracutdir=DIR    install dracut helpers [default=check]

When rebuilding using the source packages the per-distribution
default values specified in the spec file will be used.  This is
the preferred way to build packages for a distribution but the
ability to override the defaults is provided as a convenience.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1874