Throw specific error when ':' exists in PV names

While ':' is not actually a supporte character in PV names (it has a
special meaning for commands like lvcreate), we should throw specific
errors for this case instead of generic “Can't create LV”.

This patch does two things:

- modifies the separator used when listing PVs to be '|' such that we
  can actually parse ':' as part of PV names
- check if any of the discovered PVs have ':' in their name when
  creating LVs, and if so throw a specific error

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>