hg: avoid auto sharing when the clone destination is remote
Before this patch, when auto sharing is enabled, 'hg.clone()' tries to
create local clone regardless of locality of the clone destination on
the host, and causes failure.
To avoid auto sharing when the clone destination is remote, this patch
adds examination of 'islocal(dest)' before auto sharing in
'hg.clone()'.
'islocal(dest)' is examined after 'sharepool', because:
- the former is more expensive than the latter
- without enabling share extension, the later is always negative