SYS_VARS SUITE IN MTR 

Description:
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In mysql-test/suite/sys_vars/t/*.test, in each file there should be a test
that tries to assign out-of-bounds values to the variables, and then does a
SHOW to ensure that it is being clamped to the min or max.

Also, there should be a test that tries to assign SET GLOBAL (name_of_var)=
DEFAULT.

Suggested Fix:
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Review the entire sys_vars suite and make the
necessary enhancements.