Fix 'rename workspace to tosomething'

Fix 'rename workspace to tosomething'

This patch fixes the issue #2802 (https://github.com/i3/i3/issues/2802).

1). Revise the state machine for the 'rename workspace' command.
    These scenarios are considered:
    a). 'rename workspace to to bla'
        state transitions: RENAME -> RENAME_WORKSPACE -> RENAME_WORKSPACE_LIKELY_TO -> RENAME_WORKSPACE_LIKELY_TO_NEW_NAME
    b). 'rename workspace to tosomething'
        state transitions: RENAME -> RENAME_WORKSPACE -> RENAME_WORKSPACE_LIKELY_TO
    c). 'rename workspace to to'
        state transitions: RENAME -> RENAME_WORKSPACE -> RENAME_WORKSPACE_LIKELY_TO
    d). 'rename workspace to bla'
        state transitions: RENAME -> RENAME_WORKSPACE -> RENAME_WORKSPACE_LIKELY_TO
    e). 'rename workspace bla to foo'
        state transitions: RENAME -> RENAME_WORKSPACE -> RENAME_WORKSPACE_TO -> RENAME_WORKSPACE_TO_NEW_NAME

2). Add a test case in 117-workspace.t for the scenario b.