Extract common parts from isolation2 makefile into global makefile

It makes isolation2 framework more consistent with pg_regress and
isolation in terms of how it is invoked from the build system.

src/Makefile.global.in

@@ -712,6 +712,11 @@ pg_isolation_regress_installcheck = \
     --bindir='$(bindir)' \
     $(pg_regress_locale_flags) $(EXTRA_REGRESS_OPTS)
 
+pg_isolation2_regress_installcheck = \
+    $(top_builddir)/src/test/isolation2/pg_isolation2_regress \
+    --inputdir=$(srcdir) \
+    --bindir= \
+    $(pg_regress_locale_flags) $(EXTRA_REGRESS_OPTS)
 ##########################################################################
 #
 # Customization

src/test/isolation2/Makefile

@@ -61,7 +61,7 @@ clean distclean:
 install: all gpdiff.pl gpstringsubs.pl
 
 installcheck: install
-	./pg_isolation2_regress $(EXTRA_REGRESS_OPTS) --init-file=$(top_builddir)/src/test/regress/init_file --init-file=./init_file_isolation2 --bindir='$(bindir)' --inputdir=$(srcdir) --load-extension=gp_inject_fault --schedule=$(srcdir)/isolation2_schedule
+	$(pg_isolation2_regress_installcheck) --init-file=$(top_builddir)/src/test/regress/init_file --init-file=./init_file_isolation2 --schedule=$(srcdir)/isolation2_schedule
 
 installcheck-resgroup: install
-	./pg_isolation2_regress $(EXTRA_REGRESS_OPTS) --init-file=$(top_builddir)/src/test/regress/init_file --init-file=./init_file_resgroup --bindir='$(bindir)' --inputdir=$(srcdir) --dbname=isolation2resgrouptest --load-extension=gp_inject_fault --schedule=$(srcdir)/isolation2_resgroup_schedule
+	$(pg_isolation2_regress_installcheck) --init-file=$(top_builddir)/src/test/regress/init_file --init-file=./init_file_resgroup --dbname=isolation2resgrouptest --schedule=$(srcdir)/isolation2_resgroup_schedule