torture_session.c: Append a '\0' before string comparison

ssh_channel_read() reads the data into the buffer, but doesn't
append a '\0' after it. When the buffer is asserted to be equal to
a string further in the test, the assertion could fail if the byte
after the data stored in the buffer doesn't contain '\0' (and it mayn't)

This commit appends a '\0' after the data read into the buffer before
comparing it with a string.

Signed-off-by: Eshan Kelkar <eshankelkar@galorithm.com>
Reviewed-by: Sahana Prasad <sahana@redhat.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

tests/client/torture_session.c

@@ -471,6 +471,8 @@ torture_channel_read_stderr(void **state)
     /* Everything in stderr */
     rc = ssh_channel_read(channel, buffer, sizeof(buffer), 1);
     assert_int_equal(rc, strlen("ABCD"));
+
+    buffer[rc] = '\0';
     assert_string_equal("ABCD", buffer);
 
     ssh_channel_free(channel);