Added test 626 to reproduce an infinite loop when given an invalid

SFTP quote command reported by Vincent Le Normand, but left it disabled.

tests/data/test626

@@ -0,0 +1,42 @@
+<testcase>
+<info>
+<keywords>
+SFTP
+pre-quote
+FAILURE
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+sftp
+</server>
+ <name>
+SFTP invalid quote command
+ </name>
+ <command>
+--key curl_client_key --pubkey curl_client_key.pub -u %USER: -Q "invalid-command foo bar" sftp://%HOSTIP:%SSHPORT%PWD/log/file626.txt
+</command>
+<file name="log/file626.txt">
+Test file for rename test
+</file>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<file name="log/file626-renamed.txt">
+Test file for rename test
+</file>
+<valgrind>
+disable
+</valgrind>
+</verify>
+</testcase>