Continuations: Mixed mode continuations fail for COALESCE

[ohadzeliger]

Forcing a continuation on a COALESCE query in mixed mode causes the query to fail

Steps To Reproduce:

1. Look at functions.yamsql
2. Change the test to look like:

3.   - query: select coalesce(null, null, 5), coalesce(null, 1, null), coalesce(null, a1, a8) from A
   

   • maxRows: 1
   • result: [{_0: 5, _1: 1, _2: 1.0}]
   • result: []
4. This test passes in single-server tests but fails in mixed mode tests
5. The failure is “cannot continue query due to mismatch between serialized and actual plan hash”