Since r221218 rman_manage_region(9) actually honors rm_start and rm_end which may cause problems when these contain garbage so zero the range descriptors embedding the rmans when allocating them.
Since r221218 rman_manage_region(9) actually honors rm_start and rm_end
which may cause problems when these contain garbage so zero the range
descriptors embedding the rmans when allocating them.

Approved by:	re (kib)
MFC after:	3 days

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