tests: run app-driven sftp in a block build

The non-blocking app-driven case runs under WOLFSSH_TEST_BLOCK again,
reverting ba899603. It deadlocks there until ssh_worker() waits on the
write side for a send wolfSSH_worker() reported through ssh->error, so
this wants PR 1251 landed with the wantWrite arm kept.

scripts/sftp.test

@@ -6,7 +6,6 @@ no_pid=-1
 server_pid="$no_pid"
 ready_file="$PWD/wolfssh_sftp_ready$$"
 nonblockingOnly=0
-blockBuild=0
 
 [ ! -x ./examples/sftpclient/wolfsftp ] && echo && echo "wolfSFTP client doesn't exist" && exit 1
 
@@ -28,7 +27,6 @@ if echo "$WOLFSSH_OPTIONS" | grep -qx "TEST_BLOCK"
 then
     echo "macro WOLFSSH_TEST_BLOCK was used"
     nonblockingOnly=1
-    blockBuild=1
 fi
 
 #echo "ready file $ready_file"
@@ -134,24 +132,19 @@ if [ "$nonblockingOnly" = 0 ]; then
 fi
 
 # The same handoff on a non-blocking server, which reaches the accept call's
-# want-read and want-write retries. Held out of a forced-blocking build: the
-# two ends deadlock there, the server parked in DoReceive with output it owes
-# still queued, which is a defect of its own rather than this case failing.
-if [ "$blockBuild" = 0 ]; then
-    echo "Test non blocking connection to an app-driven server"
-    ./examples/echoserver/echoserver -A -N -1 -R "$ready_file" &
-    server_pid=$!
-    create_port
-    echo "exit" | ./examples/sftpclient/wolfsftp -N -u jill -P upthehill \
-        -p "$port"
-    RESULT=$?
-    remove_ready_file
-    if [ $RESULT -ne 0 ]; then
-        echo
-        echo "failed to connect to non blocking app-driven server"
-        do_cleanup
-        exit 1
-    fi
+# want-read and want-write retries.
+echo "Test non blocking connection to an app-driven server"
+./examples/echoserver/echoserver -A -N -1 -R "$ready_file" &
+server_pid=$!
+create_port
+echo "exit" | ./examples/sftpclient/wolfsftp -N -u jill -P upthehill -p "$port"
+RESULT=$?
+remove_ready_file
+if [ $RESULT -ne 0 ]; then
+    echo
+    echo "failed to connect to non blocking app-driven server"
+    do_cleanup
+    exit 1
 fi
 
 # Test want write return from highwater callback