fix crashes on error'd WCS getcoverage requests (#4714)

initialise msWCSGetCoverageMetadata20 to NULL to avoid memory failures
on error
Merge pull request #4714 from tbonfort/b4714-wcs-mem-crash

Fix crashes on failed WCS request (#4714)
Correcting version attribute in WCS exceptions (#4717).
update msautotest submodule
update msautotest submodule
Merge pull request #4718 from EOX-A/version_attribute

Adjust version attribute in WCS exceptions (#4717)
Merge branch 'branch-6-2'
Update msautotest submodule for #4717.

Conflicts:
	msautotest