qemu: remove unnecessary virBufferFreeAndReset() after virCommandAddArgBuffer()

The latter function is guaranteed to always clear out the virBuffer
anyway, so this is redundant and could add to extra cargo-cult code if
used as an example.

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/qemu/qemu_command.c

@@ -9080,7 +9080,6 @@ qemuBuldDomainLoaderPflashCommandLine(virCommandPtr cmd,
     virCommandAddArgBuffer(cmd, &buf);
 
     if (loader->nvram) {
-        virBufferFreeAndReset(&buf);
         virBufferAddLit(&buf, "file=");
         virQEMUBuildBufferEscapeComma(&buf, loader->nvram);
         virBufferAsprintf(&buf, ",if=pflash,format=raw,unit=%d", unit);