report: fix thin external snapshot identification for lv_layout and lv_type fields

report: fix thin external snapshot identification for lv_layout and lv_type fields

Thin snapshots having external origins missed the "snapshot" keyword for
lv_type field. Also, thin external origins which are thin devices (from
another pool) were not recognized properly.

For example, external origin itself can be either non-thin volume (lvol0
below) or it can be a thin volume from another pool (lvol3 below):

Before this patch:

$ lvs -o name,vg_name,attr,pool_lv,origin,layout,type
  Internal error: Failed to properly detect layout and type for for LV vg/lvol3
  Internal error: Failed to properly detect layout and type for for LV vg/lvol3
  LV    VG     Attr       Pool  Origin Layout     Type
  lvol0 vg     ori-------              linear     external,origin,thin
  lvol2 vg     Vwi-a-tz-- pool  lvol0  thin       thin
  lvol3 vg     ori---tz-- pool         unknown    external,origin,thin,thin
  lvol4 vg     Vwi-a-tz-- pool1 lvol3  thin       thin
  pool  vg     twi-a-tz--              pool,thin  pool,thin
  pool1 vg     twi-a-tz--              pool,thin  pool,thin

- lvol2 as well as lvol4 have missing "snapshot" in type field
- lvol3 has unrecognized layout (should be "thin"), but has double
  "thin" in lv_type which is incorrect
- (also there's double "for" in the internal error message)

With this patch applied:

$ lvs -o name,vg_name,attr,pool_lv,origin,layout,type
  LV    VG     Attr       Pool  Origin Layout     Type
  lvol0 vg     ori-------              linear     external,origin,thin
  lvol2 vg     Vwi-a-tz-- pool  lvol0  thin       snapshot,thin
  lvol3 vg     ori---tz-- pool         thin       external,origin,thin
  lvol4 vg     Vwi-a-tz-- pool1 lvol3  thin       snapshot,thin
  pool  vg     twi-a-tz--              pool,thin  pool,thin
  pool1 vg     twi-a-tz--              pool,thin  pool,thin