FIX: use /usr/bin/env bash in shebang

FIX: grpc/grpc-go#1023

Signed-off-by: Thibault Riviere <thibault.riviere@scality.com>

codegen.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # This script serves as an example to demonstrate how to generate the gRPC-Go
 # interface and the related messages from .proto file.

coverage.sh

@@ -1,4 +1,5 @@
-#!/bin/bash
+#!/usr/bin/env bash
+
 
 set -e