LU-8653 lod: use stripe_count instead of stripe_nr

LU-8653 lod: use stripe_count instead of stripe_nr

Replace the use of stripenr and stripecnt in the code with
stripe_count to be consistent the rest of the code.

Introduce LOV_PATTERN_NONE instead of using "0" around the
code to indicate no layout has been specified.

Introduce LOV_PATTERN_DEFAULT to indicate the entire layout
is unset, instead of using "0xffffffff" in the code.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I6056aebc1a381b09c1a436fb4a7986a51f3ebbe5
Reviewed-on: https://review.whamcloud.com/26681
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Steve Guminski <stephenx.guminski@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>