... Without appending the 'ro' to mount options of '/' mount point the
  system will be still mounted as read-write, even when READONLY=yes.

$" is a BASH extension to translate text.
Replace the shebang with /bin/bash to avoid parsing errors,
as even BASH has a POSIX compliant mode when run as sh.

Signed-off-by: Matteo Croce <mcroce@redhat.com>

  https://bugzilla.redhat.com/show_bug.cgi?id=1512688

network-functions uses awk to tranform the mac address to upper case.
Replace awk with tr which is two order of magnitude faster:

    $ time awk '{ print toupper($0) }' </usr/share/dict/words >/dev/null

    real    0m0,227s
    user    0m0,224s
    sys     0m0,004s
    $ time tr '[a-z]' '[A-Z]' </usr/share/dict/words >/dev/null

    real    0m0,005s
    user    0m0,000s
    sys     0m0,005s

Also use here-strings instead of spawning a subshell and a pipe.

Signed-off-by: Matteo Croce <mcroce@redhat.com>

  Instead of displaying messages without context, like this:

  ./network-functions: line 571: echo: write error: Invalid argument
  ./network-functions: line 598: echo: write error: Permission denied

  We will now display pretty error messages (via net_log) about what has
  actually failed...

  Previously, there were 2 additional conditions related to this part of
  code, but they were removed in time, so this last condition has
  remained an artifact and is de-facto obsolete.

  However, the 'pidof -x dhclient' condition could cause the network
  service to hang on stop/restart when processes were executed from a
  network share... Removing that condition should hypothetically fix it.

  Since we are using systemd, the Default-Start/Stop keywords were
  omitted. Basically the LSB header is quite similar to LSB header of
  network service...

  The tabs & spaces mixture caused bad script conversion and breaking
  the script completely...

  Also, the code has been fixed to comply with PEP8 specification.
  More info: https://fedoraproject.org/wiki/FinalizingFedoraSwitchtoPython3