Avoid timing issue in diskless-load-swapdb test

[enjoy-binbin]

Since we paused the primary node earlier, the replica may enter
cluster down due to primary node pfail. Here set allow read to
prevent subsequent read errors.

[enjoy-binbin]

failed CI:
https://github.com/valkey-io/valkey/actions/runs/10987837289/job/30503299419#step:5:4849

[exception]: Executing test client: CLUSTERDOWN The cluster is down.
CLUSTERDOWN The cluster is down
    while executing
"$replica get $slot0_key"
    ("uplevel" body line 70)
    invoked from within
"uplevel 1 $code"
    (procedure "test" line 58)
    invoked from within
"test "Main db not affected when fail to diskless load" {

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.62%. Comparing base (bf8183d) to head (dcdf581).
Report is 8 commits behind head on unstable.

Additional details and impacted files

@@            Coverage Diff            @@
##           unstable    #1077   +/-   ##
=========================================
  Coverage     70.61%   70.62%           
=========================================
  Files           114      114           
  Lines         61695    61695           
=========================================
+ Hits          43568    43573    +5     
+ Misses        18127    18122    -5     

see 11 files with indirect coverage changes