Remove vm destroy right after vm start to avoid destroy cmd failure

[liang-cong-red-hat]

vm destroy right after vm start may fail destroy cmd (when vm initial time need longer time, for instance using hugepage), then the failed destroy cmd may impact following guest save cmd.

Resuts: run 20 times all pass: (1/1) type_specific.io-github-autotest-libvirt.memory.backing.lifecycle.memory_hugepage.default_hugepage_size: PASS (143.65 s)