Fix name collision between concurrent regression tests.

Commit f5bcd398 introduced a test using
a table named "circles" in inherit.sql.  Unfortunately, the concurrently
executed constraints test was already using that table name, so the
parallel regression tests would sometimes fail.  Rename table to dodge
the problem.  Per buildfarm.

src/test/regress/expected/inherit.out

@@ -1009,41 +1009,41 @@ Has OIDs: no
 
 DROP TABLE test_constraints_inh;
 DROP TABLE test_constraints;
-CREATE TABLE circles (
+CREATE TABLE test_ex_constraints (
     c circle,
     EXCLUDE USING gist (c WITH &&)
 );
-NOTICE:  CREATE TABLE / EXCLUDE will create implicit index "circles_c_excl" for table "circles"
-CREATE TABLE circles_inh () INHERITS (circles);
-\d+ circles
-                       Table "public.circles"
+NOTICE:  CREATE TABLE / EXCLUDE will create implicit index "test_ex_constraints_c_excl" for table "test_ex_constraints"
+CREATE TABLE test_ex_constraints_inh () INHERITS (test_ex_constraints);
+\d+ test_ex_constraints
+                 Table "public.test_ex_constraints"
  Column |  Type  | Modifiers | Storage | Stats target | Description 
 --------+--------+-----------+---------+--------------+-------------
  c      | circle |           | plain   |              | 
 Indexes:
-    "circles_c_excl" EXCLUDE USING gist (c WITH &&)
-Child tables: circles_inh
+    "test_ex_constraints_c_excl" EXCLUDE USING gist (c WITH &&)
+Child tables: test_ex_constraints_inh
 Has OIDs: no
 
-ALTER TABLE circles DROP CONSTRAINT circles_c_excl;
-\d+ circles
-                       Table "public.circles"
+ALTER TABLE test_ex_constraints DROP CONSTRAINT test_ex_constraints_c_excl;
+\d+ test_ex_constraints
+                 Table "public.test_ex_constraints"
  Column |  Type  | Modifiers | Storage | Stats target | Description 
 --------+--------+-----------+---------+--------------+-------------
  c      | circle |           | plain   |              | 
-Child tables: circles_inh
+Child tables: test_ex_constraints_inh
 Has OIDs: no
 
-\d+ circles_inh
-                     Table "public.circles_inh"
+\d+ test_ex_constraints_inh
+               Table "public.test_ex_constraints_inh"
  Column |  Type  | Modifiers | Storage | Stats target | Description 
 --------+--------+-----------+---------+--------------+-------------
  c      | circle |           | plain   |              | 
-Inherits: circles
+Inherits: test_ex_constraints
 Has OIDs: no
 
-DROP TABLE circles_inh;
-DROP TABLE circles;
+DROP TABLE test_ex_constraints_inh;
+DROP TABLE test_ex_constraints;
 -- Test non-inheritable foreign key contraints
 CREATE TABLE test_primary_constraints(id int PRIMARY KEY);
 NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test_primary_constraints_pkey" for table "test_primary_constraints"

src/test/regress/sql/inherit.sql

@@ -302,17 +302,17 @@ ALTER TABLE ONLY test_constraints DROP CONSTRAINT test_constraints_val1_val2_key
 DROP TABLE test_constraints_inh;
 DROP TABLE test_constraints;
 
-CREATE TABLE circles (
+CREATE TABLE test_ex_constraints (
     c circle,
     EXCLUDE USING gist (c WITH &&)
 );
-CREATE TABLE circles_inh () INHERITS (circles);
-\d+ circles
-ALTER TABLE circles DROP CONSTRAINT circles_c_excl;
-\d+ circles
-\d+ circles_inh
-DROP TABLE circles_inh;
-DROP TABLE circles;
+CREATE TABLE test_ex_constraints_inh () INHERITS (test_ex_constraints);
+\d+ test_ex_constraints
+ALTER TABLE test_ex_constraints DROP CONSTRAINT test_ex_constraints_c_excl;
+\d+ test_ex_constraints
+\d+ test_ex_constraints_inh
+DROP TABLE test_ex_constraints_inh;
+DROP TABLE test_ex_constraints;
 
 -- Test non-inheritable foreign key contraints
 CREATE TABLE test_primary_constraints(id int PRIMARY KEY);