esx: replace some VIR_FREE with g_clear_pointer(x, g_free)

esx: replace some VIR_FREE with g_clear_pointer(x, g_free)

These are all cases when 1) the pointer is passed by reference from
the caller (ie.e. **) and expects it to be NULL on return if there is
an error, or 2) the variable holding the pointer is being checked or
re-used in the same function, but not right away.

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>