Replace one-line if condition with long syntax for functions.sh lib

One-line condition lead to function exit with status of condition itself.
With enabled set -e - it's leading to aborting whole script.

Change-Id: Icd65a7cf0586f49f73a2af1c411a83d007417744
Related-Prod: PROD-30834
diff --git a/predefine-vm/functions.sh b/predefine-vm/functions.sh
index ed2ad0f..d5b1cec 100644
--- a/predefine-vm/functions.sh
+++ b/predefine-vm/functions.sh
@@ -36,9 +36,15 @@
 function prereq_check {
     local slave=${1}
     check_packages "${slave}"
-    [[ "${VM_MGM_BRIDGE_DISABLE}" =~ [Ff]alse ]] && check_bridge_exists "${VM_MGM_BRIDGE_NAME}" "VM_MGM_BRIDGE_DISABLE"
-    [[ "${VM_CTL_BRIDGE_DISABLE}" =~ [Ff]alse ]] && check_bridge_exists "${VM_CTL_BRIDGE_NAME}" "VM_CTL_BRIDGE_DISABLE"
-    [[ -n "${NON_DEFAULT_LIBVIRT_DIR}" ]] && echo "All files will be saved under ${NON_DEFAULT_LIBVIRT_DIR} directory. Make sure that libvirt-qemu:kvm has access rights to that path."
+    if [[ "${VM_MGM_BRIDGE_DISABLE}" =~ [Ff]alse ]]; then
+      check_bridge_exists "${VM_MGM_BRIDGE_NAME}" "VM_MGM_BRIDGE_DISABLE"
+    fi
+    if [[ "${VM_CTL_BRIDGE_DISABLE}" =~ [Ff]alse ]]; then
+      check_bridge_exists "${VM_CTL_BRIDGE_NAME}" "VM_CTL_BRIDGE_DISABLE"
+    fi
+    if [[ -n "${NON_DEFAULT_LIBVIRT_DIR}" ]]; then
+      echo "All files will be saved under ${NON_DEFAULT_LIBVIRT_DIR} directory. Make sure that libvirt-qemu:kvm has access rights to that path."
+    fi
 }
 
 function do_create_new_network {