proxy: re-use proxy connections (regression)

When checking for a connection to re-use, a proxy-using request must
check for and use a proxy connection and not one based on the host
name!

Added test 1421 to verify

Bug: http://curl.haxx.se/bug/view.cgi?id=1492

tests/data/Makefile.inc

@@ -142,7 +142,7 @@ test1396 test1397 test1398 \
 \
 test1400 test1401 test1402 test1403 test1404 test1405 test1406 test1407 \
 test1408 test1409 test1410 test1411 test1412 test1413 test1414 test1415 \
-test1416 test1417 test1418 test1419 test1420 \
+test1416 test1417 test1418 test1419 test1420 test1421 \
 \
 test1428 test1429 test1430 test1431 test1432 test1433 test1434 test1435 \
 test1436 \

tests/data/test1421

@@ -0,0 +1,72 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+HTTP proxy
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.1 200 OK
+Uknown-header: blrub
+Content-Length: 6
+
+-foo-
+</data>
+
+<servercmd>
+connection-monitor
+</servercmd>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+http
+</server>
+ <name>
+Re-using HTTP proxy connection for two different host names
+ </name>
+ <command>
+--proxy http://%HOSTIP:%HTTPPORT http://test.remote.haxx.se.1421:8990/ http://different.remote.haxx.se.1421:8990
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<stdout>
+HTTP/1.1 200 OK
+Uknown-header: blrub
+Content-Length: 6
+
+-foo-
+HTTP/1.1 200 OK
+Uknown-header: blrub
+Content-Length: 6
+
+-foo-
+</stdout>
+<strip>
+^User-Agent:.*
+</strip>
+<protocol>
+GET http://test.remote.haxx.se.1421:8990/ HTTP/1.1
+Host: test.remote.haxx.se.1421:8990
+Accept: */*
+Proxy-Connection: Keep-Alive
+
+GET http://different.remote.haxx.se.1421:8990/ HTTP/1.1
+Host: different.remote.haxx.se.1421:8990
+Accept: */*
+Proxy-Connection: Keep-Alive
+
+[DISCONNECT]
+</protocol>
+</verify>
+</testcase>