Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/sysbench/versions.

<details><summary>Version release notes (from GitHub)</summary>
	* version 1.0.15
	* CI/build/packaging: add Fedora 28
	* CI/build/packaging: add Ubuntu Bionic
	* CI/build/packaging: remove Fedora 26 (EOL)
	* CI/build/packaging: remove Debian Wheezy (EOL)
	* fileio: fix GH-229 (--file-fsync-freq=0 seems to prevent
	fsync() at the end of the test)
	* command line: improve parsing of boolean command line options
	* tests: fix GH-220 (Testsuite api_sql_mysql.t failed ...)
	* tests: fix GH-223 (test failure on ppc64)
	* tests: fix opt_help.t to pass when the binary is not
	configured with MySQL support
	* MySQL driver: use it by default in DB benchmarks
</details>

These checks were done:

- built on NixOS
- /nix/store/jfyhnvp5696s1cjn64fxp5ir072m7h35-sysbench-1.0.15/bin/sysbench passed the binary check.
- 1 of 1 passed binary check by having a zero exit code.
- 1 of 1 passed binary check by having the new version present in output.
- found 1.0.15 with grep in /nix/store/jfyhnvp5696s1cjn64fxp5ir072m7h35-sysbench-1.0.15
- directory tree listing: https://gist.github.com/2d15615806f49f153b03e6495af3654b
- du listing: https://gist.github.com/6d323aaf15bf22506caed9176fe9b034

sysbench: 1.0.14 -> 1.0.15