rsync_protocol(): fix regex for bash 3.2

Thanks to maswan for the notice:
etc/common: line 239: unexpected argument `(' to conditional binary operator'

Introduced by 8d734b / a37134

1 files changed, 3 insertions, 2 deletions

diff --git a/etc/common b/etc/common
index de3cfac..49ca038 100644
--- a/etc/common
+++ b/etc/common
@@ -236,8 +236,9 @@ savelog() {
 # Return rsync version
 rsync_protocol() {
     RSYNC_VERSION="$(${RSYNC} --version)"
-    if [[ $RSYNC_VERSION =~ (protocol[ ]+version[ ]+([0-9]+)) ]]; then
+    RSYNC_REGEX="(protocol[ ]+version[ ]+([0-9]+))"    
+    if [[ ${RSYNC_VERSION} =~ ${RSYNC_REGEX} ]]; then
         echo ${BASH_REMATCH[2]}
     fi
-    unset RSYNC_VERSION
+    unset RSYNC_VERSION RSYNC_REGEX
 }