vgimportclone: replace awk with dumpconfig to generate temporary lvm.conf for vgimpor...

vgimportclone: replace awk with dumpconfig to generate temporary lvm.conf for vgimportclone

With current dumpconfig, we can generate lvm.conf easily - we can merge
current lvm.conf with the config given on cmd line:
  lvm dumpconfig --mergedconfig --config "..."

This is a bit simpler than using awk and it also avoids problems when some of
the configuration is missing in existing lvm.conf file and hardcoded defaults
are used instead. The dumpconfig handles this transparently.