vtc: Increase stack size for 32bit systems in e29

This test case has been failing for a while in continuous integration
and trying to bisect the change that triggered a stack overflow for our
Ubuntu 18.04 job I wasn't able to make it pass, even for the commit
where it first landed.

Something must have happened outside of Varnish to consume more stack.

bin/varnishtest/tests/e00029.vtc

@@ -16,7 +16,9 @@ server s1 {
 	chunkedlen 0
 } -start
 
-varnish v1 -arg "-p feature=+esi_include_onerror" -vcl+backend {
+varnish v1 -cliok "param.set thread_pool_stack 80k"
+varnish v1 -cliok "param.set feature +esi_include_onerror"
+varnish v1 -vcl+backend {
 	sub vcl_backend_response {
 		set beresp.do_esi = true;
 		set beresp.do_gzip = true;
@@ -38,4 +40,4 @@ client c1 {
 	rxresp
 } -run
 
-logexpect l1 -wait
\ No newline at end of file
+logexpect l1 -wait