Use factoryreset as a workaround to reduce the delay of reforming a
network

There's a defect in ot-daemon that re-forming a network after erasing
the persistent data will take longer delay. We can use the
`factoryreset` command to work this around so that the test cases take
less time.

Bug: 323301831
Bug: 328235705

Change-Id: I36e67fe0f7f1165a03e71397065a6166117acadb
2 files changed