vchoi_fork

[svn-r2861] Purpose:
    Bug fix.
Description:
    When writing data and the dataset needed to be extended, the write call
    ended up using the old dataspace extents (prior to the dataspace extend)
    and bad parameters would get into the I/O channel, eventually causing it
    to dump core.
Solution:
    Every time a dataset is extended, throw away the previous dataspace
    information and re-retrieve it.
Platforms tested:
    FreeBSD 4.1.1 (hawkwind)