Fix races in scripts.base.frameworks.intel.cluster-transparency-with-proxy test

This test was unstable for two reasons:

- Nothing verified whether the two workers had checked in with the proxy,
meaning that messages between the workers and proxies could get lost. This adds
an extra node_up event that the proxy generates synthetically, with values
recognizable to the manager, once the proxy sees both workers connected. This is
a test-level workaround for what should really be a cluster-is-ready event in
the cluster framework proper.

- More subtle: the Intel framework makes the manager send its current
min_data_store to newly connected workers, which in the case of this tests
introduces a race: since the data store, arriving at the worker, replaces the
existing value, it could actually remove already established items if timing was
right. This would lead to the count in the test reaching 3, assuming that 3
intel items are available, when in reality it was less, causing the
Intel::seen() call to do nothing. We now disable the sending of the data store
upon connect, via the global added in the previous commit.

This also expands the test slightly so that both workers call Intel::seen() for
the items inserted by the other worker. This is added validation for the second
point above, because in the presence of that race one occasionally sees one log
entry make it, and the other fail.

testing/btest/Baseline/scripts.base.frameworks.intel.cluster-transparency-with-proxy/manager-1.intel.log

@@ -1,4 +1,5 @@
 ### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+### NOTE: This file has been sorted with diff-sort.
 #separator \x09
 #set_separator	,
 #empty_field	(empty)
@@ -7,5 +8,6 @@
 #open XXXX-XX-XX-XX-XX-XX
 #fields	ts	uid	id.orig_h	id.orig_p	id.resp_h	id.resp_p	seen.indicator	seen.indicator_type	seen.where	seen.node	matched	sources	fuid	file_mime_type	file_desc
 #types	time	string	addr	port	addr	port	string	enum	enum	string	set[enum]	set[string]	string	string	string
-XXXXXXXXXX.XXXXXX	-	-	-	-	-	123.123.123.123	Intel::ADDR	Intel::IN_ANYWHERE	worker-2	Intel::ADDR	worker-1	-	-	-
 #close XXXX-XX-XX-XX-XX-XX
+XXXXXXXXXX.XXXXXX	-	-	-	-	-	123.123.123.123	Intel::ADDR	Intel::IN_ANYWHERE	worker-2	Intel::ADDR	worker-1	-	-	-
+XXXXXXXXXX.XXXXXX	-	-	-	-	-	4.3.2.1	Intel::ADDR	Intel::IN_ANYWHERE	worker-1	Intel::ADDR	worker-2	-	-	-

testing/btest/Baseline/scripts.base.frameworks.intel.cluster-transparency-with-proxy/worker-1..stdout

@@ -4,3 +4,4 @@ new_indicator: 1.2.3.4 inserted by manager
 new_indicator: 123.123.123.123 inserted by worker-1
 new_indicator: 4.3.2.1 inserted by worker-2
 new_item triggered for 123.123.123.123 by worker-1 on worker-1
+seeing 4.3.2.1

testing/btest/Baseline/scripts.base.frameworks.intel.cluster-transparency-with-proxy/worker-2..stdout

@@ -1,7 +1,7 @@
 ### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
 ### NOTE: This file has been sorted with diff-sort.
-Doing a lookup
 new_indicator: 1.2.3.4 inserted by manager
 new_indicator: 123.123.123.123 inserted by worker-1
 new_indicator: 4.3.2.1 inserted by worker-2
 new_item triggered for 4.3.2.1 by worker-2 on worker-2
+seeing 123.123.123.123