vgimporeclone: use correct cache dir path

vgimporeclone: use correct cache dir path

Commit 00b36ef06acb15c82d7c9b37872753f02c638316 had a typo
and missed '{' for shell variable, thus command used slightly
different 'tmp' dir name for cache dir (with extra '}').

Such change was unnoticed until a recent fix in persistent
filter, lvm2 missed to update cache file when --config
was specified.

The result was, /tmp dir was accumulating snap.XXXXX} dirs when
running vgimportclose  script.