pgsql: Fix the SharedFileSetUnregister API.

Fix the SharedFileSetUnregister API.

Commit 808e13b282 introduced a few APIs to extend the existing Buffile
interface. In SharedFileSetDeleteOnProcExit, it tries to delete the list
element while traversing the list with 'foreach' construct which makes the
behavior of list traversal unpredictable.

Author: Amit Kapila
Reviewed-by: Dilip Kumar
Tested-by: Dilip Kumar and Neha Sharma
Discussion: https://postgr.es/m/CAA4eK1JhLatVcQ2OvwA_3s0ih6Hx9+kZbq107cXVsSWWukH7vA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4ab77697f67aa5b90b032b9175b46901859da6d7

Modified Files
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src/backend/storage/file/sharedfileset.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)