STABLE12-linux-rework-signal-blocking-for-afsdb-handler-and-clean-up-osi-invisible...

STABLE12-linux-rework-signal-blocking-for-afsdb-handler-and-clean-up-osi-invisible-before-im-completely-blind-20020123

based on suggestion from kolya@mit.edu

and osi_Invisible cleanup so ifdef logic would be more clear

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This delta was composed from multiple commits as part of the CVS->Git migration.
The checkin message with each commit was inconsistent.
The following are the additional commit messages.
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don't do this in userland cache manager

(cherry picked from commit 1f3f7bc3efea3ffca469fbfe090953dcaa668799)