vtsl: eliminate 'data->state.ssl_scache'

Keeping the relevant 'ssl_scache' in 'data->state' leads to problems
when the owner of the cache is cleaned up and this reference is left
dangling.

Remove the ref entirely and always find the ssl_scache at the current
share or multi.

Folded in #16260 (test 3208) to verify this fixes the bug with a
dangling reference when an easy handle is used with easy_perform first
and in a multi_perform after.

Ref: #16236
Closes #16261

tests/data/Makefile.am

@@ -272,6 +272,6 @@ test3032 \
 \
 test3100 test3101 test3102 test3103 test3104 test3105 \
 test3200 \
-test3201 test3202 test3203 test3204 test3205 test3207
+test3201 test3202 test3203 test3204 test3205 test3207 test3208
 
 EXTRA_DIST = $(TESTCASES) DISABLED

tests/data/test3208

@@ -0,0 +1,60 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+libtest
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Last-Modified: Tue, 13 Jun 2000 12:10:00 GMT
+ETag: "21025-dc7-39462498"
+Accept-Ranges: bytes
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+Funny-head: yesyes
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+https
+</server>
+# tool is what to use instead of 'curl'
+<tool>
+lib%TESTNUMBER
+</tool>
+
+<name>
+curl_easy_perform then curl_multi_perform the same handle
+</name>
+<command>
+https://%HOSTIP:%HTTPSPORT/%TESTNUMBER
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<protocol>
+GET /%TESTNUMBER HTTP/1.1
+Host: %HOSTIP:%HTTPSPORT
+Accept: */*
+
+GET /%TESTNUMBER HTTP/1.1
+Host: %HOSTIP:%HTTPSPORT
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>