Add unit test to tapPREFER_QUEUE flag

[carlhua]

Here’s the commit that added the flag: ximinez@62127d7 There are no unit tests where this flag is being exercised, including the manual tests.

Considering the tapPREFER_QUEUE flag was added in response to a critical event, I believe we should be exercising the flag during testing. Someone will need to study the code in order to identify the conditions necessary to exercise the flag.

Exported from RIPD-1792

[intelliot]

• The tapPREFER_QUEUE flag was added to the code base in response to Recent fee rises and TxQ issues #2215
• This issue was originally reported by @scottschurr

[ximinez]

The flag was removed in ae9930b, which was released in 1.8.2.