Virsh uses an error handler to save errors from libvirt. On some code
paths it's needed to clear libvirt errors and continue on fallback code
paths without reporting failure.
This patch adds function vshResetLibvirtError() that clears error
returned by libvirt and updates all places where the old two-line method
was used.
Commands to manage domain snapshot are moved from virsh.c to
virsh-snapshot.c.
* virsh.c: Remove domain snapshot commands.
* virsh-snapshot.c: New file, filled with domain snapshot commands.
* po/POTFILES.in: Add virsh-snapshot.c
* cfg.mk: Skip strcase and config.h including checking for
virsh-snapshot.c