snapshot: simplify indentation of sysinfo

snapshot: simplify indentation of sysinfo

The improvements to virBuffer, along with a paradigm shift to pass
the original buffer through rather than creating a second buffer,
allow us to shave off quite a few lines of code.

* src/util/sysinfo.h (virSysinfoFormat): Alter signature.
* src/util/sysinfo.c (virSysinfoFormat, virSysinfoBIOSFormat)
(virSysinfoSystemFormat, virSysinfoProcessorFormat)
(virSysinfoMemoryFormat): Change indentation parameter.
* src/conf/domain_conf.c (virDomainSysinfoDefFormat): Adjust
caller.
* src/qemu/qemu_driver.c (qemuGetSysinfo): Likewise.