do not produce output when using grep command

shared/macros/10-bash.jinja

@@ -1725,7 +1725,7 @@ Ensures that given mount point is in :code:`/etc/fstab`.
 mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" {{{ mount_point }}})"
 
 # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
-if ! grep "$mount_point_match_regexp" /etc/fstab; then
+if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
     # runtime opts without some automatic kernel/userspace-added defaults
     previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                 | sed -E "s/(rw|defaults|seclabel|{{{ mount_opt }}})(,|$)//g;s/,$//")
@@ -1738,7 +1738,7 @@ if ! grep "$mount_point_match_regexp" /etc/fstab; then
     fi
     echo "{{{ fs_spec }}} {{{ mount_point }}} {{{ type }}} defaults,${previous_mount_opts}{{{ mount_opt }}} 0 0" >> /etc/fstab
 # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
-elif ! grep "$mount_point_match_regexp" /etc/fstab | grep "{{{ mount_opt }}}"; then
+elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "{{{ mount_opt }}}"; then
     previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
     sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,{{{ mount_opt }}}|" /etc/fstab
 fi