scripts: widen the ready-file wait to ten seconds

The sftp, scp and get-put scripts wait for the echoserver to publish its
port before connecting. Two seconds is not enough for a libtool re-exec,
the dynamic linker and the sample-key parse with a dozen sibling test
jobs on the machine, so a parallel make check failed them at their first
scenario. Ten seconds matches what sshclient.test already allows.

- raise the three wait loops from 20 to 100 iterations of 0.1 seconds
- test -s, not -e, after the loop in scp.test and get-put.test: the
  ready file is created empty and the port written afterward, so -e can
  take a file caught mid-write and yield an empty port

scripts/get-put.test

@@ -45,12 +45,14 @@ READY_COUNTER=0
 
 
 wait_for_server() {
-    while [ ! -s "$READY_FILE" ] && [ "$READY_COUNTER" -lt 20 ]; do
+    while [ ! -s "$READY_FILE" ] && [ "$READY_COUNTER" -lt 100 ]; do
         sleep 0.1
         READY_COUNTER=$((READY_COUNTER+ 1))
     done
 
-    if test -e "$READY_FILE"
+    # -s, not -e: the echoserver creates the file empty and writes the
+    # port afterward, so -e can catch it mid-write and yield no port
+    if [ -s "$READY_FILE" ]
     then
         # get created port 0 ephemeral port
         PORT=$(cat "$READY_FILE")

scripts/scp.test

@@ -25,13 +25,15 @@ fi
 create_port() {
     # each server gets its own wait budget, the count must not carry over
     counter=0
-    while [ ! -s "$ready_file" ] && [ "$counter" -lt 20 ]; do
+    while [ ! -s "$ready_file" ] && [ "$counter" -lt 100 ]; do
         echo -e "waiting for ready file..."
         sleep 0.1
         counter=$((counter+ 1))
     done
 
-    if test -e $ready_file; then
+    # -s, not -e: the echoserver creates the file empty and writes the
+    # port afterward, so -e can catch it mid-write and yield no port
+    if [ -s "$ready_file" ]; then
         echo -e "found ready file, starting client..."
 
         # get created port 0 ephemeral port

scripts/sftp.test

@@ -35,7 +35,7 @@ create_port() {
     # counted per server start, so a slow first start cannot eat the wait
     # the later ones need
     counter=0
-    while [ ! -s "$ready_file" ] && [ "$counter" -lt 20 ]; do
+    while [ ! -s "$ready_file" ] && [ "$counter" -lt 100 ]; do
         echo "waiting for ready file..."
         sleep 0.1
         counter=$((counter+ 1))