Resolves: #1773798

Resolve: BZ #1691552

  This was causing the /etc/resolv.conf file to be always updated when
  RESOLV_MODS was not set...

  Before the commit 5d6156454bf8f6dab4a5fdd7e1bf6 we were not updating
  the /etc/resolv.conf file if the RESOLV_MODS was empty.

  See https://bugzilla.redhat.com/show_bug.cgi?id=1610411 for more info.

  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.

  For currently unknown reason the dbus-send calls will fail to set the
  firewall zone for the given interface if we omit the --print-reply
  option...

  This looks like some kind of race-condition in dbus-send, since the
  --print-reply makes the call synchronous and slower.

  Hopefully this is only a temporary workaround until DBus is fixed.

  Resolves: #1586284

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>

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

  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...

  This has been requested by our customer:
  https://bugzilla.redhat.com/show_bug.cgi?id=1542514

  Empty ${RESOLV_MODS} was causing a deletion of config files in
  /etc/ppp/peers/*

  Resolves: #155