Fix flaky test recoverseg_from_file (#10259)

After gprecoverseg, need to wait until the cluster is synchronized before
running subsequent tests.
Reviewed-by: NHubert Zhang <hzhang@pivotal.io>
Reviewed-by: NReviewed-by: Ashwin Agrawal <aagrawal@pivotal.io>

Cherry-picked from d490798b

src/test/isolation2/expected/segwalrep/recoverseg_from_file.out

@@ -115,12 +115,20 @@ SET
 -- end_ignore
 (exited with code 0)
 
+-- loop while segments come in sync
+do $$ begin /* in func */ for i in 1..120 loop /* in func */ if (select count(*) = 0 from gp_segment_configuration where content != -1 and mode != 's') then /* in func */ return; /* in func */ end if; /* in func */ perform gp_request_fts_probe_scan(); /* in func */ end loop; /* in func */ end; /* in func */ $$;
+DO
+
 -- rebalance the cluster
 !\retcode gprecoverseg -ar;
 -- start_ignore
 -- end_ignore
 (exited with code 0)
 
+-- loop while segments come in sync
+do $$ begin /* in func */ for i in 1..120 loop /* in func */ if (select count(*) = 0 from gp_segment_configuration where content != -1 and mode != 's') then /* in func */ return; /* in func */ end if; /* in func */ perform gp_request_fts_probe_scan(); /* in func */ end loop; /* in func */ end; /* in func */ $$;
+DO
+
 -- recheck gp_segment_configuration after rebalance
 SELECT dbid, role, preferred_role, content, mode, status FROM gp_segment_configuration order by dbid;
  dbid | role | preferred_role | content | mode | status 

src/test/isolation2/sql/segwalrep/recoverseg_from_file.sql

@@ -76,9 +76,33 @@ set allow_system_table_mods to false;
 -- at here
 !\retcode gprecoverseg -a;
 
+-- loop while segments come in sync
+do $$
+ begin /* in func */
+    for i in 1..120 loop /* in func */
+      if (select count(*) = 0 from gp_segment_configuration where content != -1 and mode != 's') then /* in func */
+        return; /* in func */
+      end if; /* in func */
+      perform gp_request_fts_probe_scan(); /* in func */
+    end loop; /* in func */
+  end; /* in func */
+$$;
+
 -- rebalance the cluster
 !\retcode gprecoverseg -ar;
 
+-- loop while segments come in sync
+do $$
+ begin /* in func */
+    for i in 1..120 loop /* in func */
+      if (select count(*) = 0 from gp_segment_configuration where content != -1 and mode != 's') then /* in func */
+        return; /* in func */
+      end if; /* in func */
+      perform gp_request_fts_probe_scan(); /* in func */
+    end loop; /* in func */
+  end; /* in func */
+$$;
+
 -- recheck gp_segment_configuration after rebalance
 SELECT dbid, role, preferred_role, content, mode, status FROM gp_segment_configuration order by dbid;