Add more attempts to a timing sensitive test (#8770)

tests/unit/expire.tcl

@@ -76,7 +76,7 @@ start_server {tags {"expire"}} {
         # This test is very likely to do a false positive if the
         # server is under pressure, so if it does not work give it a few more
         # chances.
-        for {set j 0} {$j < 3} {incr j} {
+        for {set j 0} {$j < 10} {incr j} {
             r del x
             r setex x 1 somevalue
             after 900
@@ -85,6 +85,9 @@ start_server {tags {"expire"}} {
             set b [r get x]
             if {$a eq {somevalue} && $b eq {}} break
         }
+        if {$::verbose} {
+            puts "millisecond expire test attempts: $j"
+        }
         list $a $b
     } {somevalue {}}