toollib: handle duplicate pvs in process_in_pv

toollib: handle duplicate pvs in process_in_pv

Processes a PV once for each time a device with its PV ID
exists on the command line.

This fixes a regression in the case where:

. devices /dev/sdA and /dev/sdB where clones (same PV ID)

. the cached VG references /dev/sdA

. before the regression, the command: pvs /dev/sdB
  would display the cached device clone /dev/sdA

. after the regression, pvs /dev/sdB would display nothing,
  causing vgimportclone /dev/sdB to fail.

. with this fix, pvs /dev/sdB displays /dev/sdA

Also, pvs /dev/sdA /dev/sdB will report two lines, one for each
device on the command line, but /dev/sdA is displayed for each.

This only works without lvmetad.