Add additional export debug and prevent duplicate Export_Ids

Ported from 1.5.x 969f09b31278ee81ec59d24d2a23a91a14715994

Signed-off-by: Frank Filz <ffilz@us.ibm.com>

Conflicts:

	src/Protocols/NFS/nfs_proto_tools.c
	src/include/nfs_exports.h
	src/support/exports.c
	src/support/nfs_export_list.c