No error checking when reading from file using zstd in pg_dump

Hello.

In src/bin/pg_dump/compress_zstd.c, the Zstd_read function always
returns true. But if you look at the Zstd_gets and Zstd_getc functions,
where Zstd_read is called via CFH->read_func, it is expected that
the Zstd_read function can also return false. In case of
a read-from-file error, the process is expected to terminate, but
pg_dump will continue the process.
I assume that after checking
if (cnt == 0)
should be
return false;

Patch attached.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Reporter: Evgeniy Gorbanev (gorbanyoves(at)basealt(dot)ru).

Organization: BaseALT (org(at)basealt(dot)ru).

Best regards,
Evgeniy