Remove force parameter from vg_remove_single, now the liblvm function.

Remove force parameter from vg_remove_single, now the liblvm function.

Move check for active LVs outside of library function.  The vgremove
liblvm function function will fail if there are active LVs.  It will
be the application's responsibility to check this condition and remove
the LVs individually before calling vgremove.  Note also that we've
duplicated the EXPORTED_VG check in vgremove_single (tools) and
vg_remove_single (library).  Duplication seemed the only option here
since we don't want to do the automatic removal of LVs (in the tools)
if the vg is exported, and we still need to protect the library call
from removal if the vg is exported.

We still need to deal with the ORPHAN lock but vg_remove_single is now
very close to our liblvm function.

TODO: Refactor lvremove in a similar way.

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>