url: make the original string get used on subsequent transfers

... since CURLOPT_URL should follow the same rules as other options:
they remain set until changed or cleared.

Added test 1551 to verify.

Fixes #1631
Closes #1632
Reported-by: Pavel Rochnyak

tests/data/Makefile.inc

@@ -165,7 +165,7 @@ test1520 test1521 \
 test1525 test1526 test1527 test1528 test1529 test1530 test1531 test1532 \
 test1533 test1534 test1535 test1536 test1537 test1538 \
 test1540 \
-test1550 \
+test1550 test1551 \
 test1600 test1601 test1602 test1603 test1604 test1605 test1606 \
 \
 test1700 test1701 test1702 \

tests/data/test1551

@@ -0,0 +1,72 @@
+<testcase>
+<info>
+<keywords>
+multi
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data>
+HTTP/1.1 302 OK
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Content-Length: 6
+Location: /15510002
+
+-foo-
+</data>
+<data2>
+HTTP/1.1 200 OK
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Content-Length: 11
+
+redirected
+</data2>
+<datacheck>
+redirected
+redirected
+</datacheck>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+# tool is what to use instead of 'curl'
+<tool>
+lib1551
+</tool>
+
+ <name>
+re-run redirected transfer without setting URL again
+ </name>
+ <command>
+http://%HOSTIP:%HTTPPORT/1551
+</command>
+</client>
+
+<verify>
+<strip>
+^User-Agent:.*
+</strip>
+<protocol>
+GET /1551 HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+
+GET /15510002 HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+
+GET /1551 HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+
+GET /15510002 HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>