pgsql: Fix LZ4 tests for remaining buffer space.

Fix LZ4 tests for remaining buffer space.

We should flush the buffer when the remaining space is less than
the maximum amount that we might need, not when it is less than or
equal to the maximum amount we might need.

Jeevan Ladhe, per an observation from me.

Discussion: http://postgr.es/m/CANm22CgVMa85O1akgs+DOPE8NSrT1zbz5_vYfS83_r+6nCivLQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/1d4be6be65ab18aa3b240d9bc912ebece255c53b

Modified Files
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src/backend/replication/basebackup_lz4.c | 4 ++--
src/bin/pg_basebackup/bbstreamer_lz4.c | 6 +++---
2 files changed, 5 insertions(+), 5 deletions(-)