test-lib: improve on previous fix

With GNU "grep" \b works but it's safer to use "egrep" which is also
POSIX rather than "grep" as not all the "grep"s out there might support \b.

License: MIT
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>

test/sharness/lib/test-lib.sh

@@ -321,7 +321,7 @@ test_should_contain() {
 test_str_contains() {
 	find=$1
 	shift
-	echo "$@" | grep "\b$find\b" >/dev/null
+	echo "$@" | egrep "\b$find\b" >/dev/null
 }
 
 disk_usage() {