update(docker/tester): split version guessing of Falco version

Needed by statically linked build of Falco.

Co-Authored-By: Leonardo Di Donato <leodidonato@gmail.com>
Signed-off-by: Leonardo Grasso <me@leonardograsso.com>

docker/tester/root/usr/bin/entrypoint

@@ -50,7 +50,8 @@ case "$CMD" in
 "test")
     if [ -z "$FALCO_VERSION" ]; then
         echo "Automatically figuring out Falco version."
-        FALCO_VERSION=$("$BUILD_DIR/$BUILD_TYPE/userspace/falco/falco" --version | head -n 1 | cut -d' ' -f3 | tr -d '\r')
+        FALCO_VERSION_FULL=$("$BUILD_DIR/$BUILD_TYPE/userspace/falco/falco" --version)
+        FALCO_VERSION=$(echo "$FALCO_VERSION_FULL" | head -n 1 | cut -d' ' -f3  | tr -d '\r')
         echo "Falco version: $FALCO_VERSION"
     fi
     if [ -z "$FALCO_VERSION" ]; then