Remove use of GNU sed features from ssl-opt.sh
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 1a9482f..7fcca68 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -326,7 +326,7 @@
 # acceptable bounds
 check_server_hello_time() {
     # Extract the time from the debug (lvl 3) output of the client
-    SERVER_HELLO_TIME="$(cat "$1" | sed -n 's/.*server hello, current time: \([0-9]\+\)$/\1/p')"
+    SERVER_HELLO_TIME="$(sed -n 's/.*server hello, current time: //p' < "$1")"
     # Get the Unix timestamp for now
     CUR_TIME=$(date +'%s')
     THRESHOLD_IN_SECS=300