Resolve: BZ #1691552

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...

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

  This is complete rework of how we generate the /etc/resolv.conf.

  Fixes:
   * always update 'nameserver' & 'search' entries when DNS* & DOMAIN
     options (respectively) were updated in ifcfg-* files
   * always update the order of 'nameserver' entries when the order of
     DNS* options was updated

  Enhancements:
   * added support for DNS3 option (equals to MAXNS value in GLIBC)
   * added logic to process duplicate DNS* options
   * added logic to process randomly omitted DNS* options (e.g. omitting
     DNS1 while specifying DNS2 and/or DNS3 will still work now)

  This work was based on these two RHEL-7.5 BZs:
  https://bugzilla.redhat.com/show_bug.cgi?id=1364895
  https://bugzilla.redhat.com/show_bug.cgi?id=1357658

  And network-scripts/network-functions was patched to use convert2sec().

  This function can be used to convert the value of its first parameter
  to a number of seconds - based on the time unit (specified as the
  second parameter).

  This is mostly useful for converting values for use with the sleep(1).

  The time units had to be manually converted from microseconds to
  seconds. Hopefully this was done right.

  The ARPUPDATE option has been introduced. It defaults to 'yes'.

  By setting the ARPUPDATE to 'no', administrator can disable
  updating neighbouring computers with ARP information about current
  NIC. This is especially needed when using LVS Load Balancing with
  Direct routing enabled.

  The way DHCP_HOSTNAME is being sent to DHCP server has been completely
  reworked...

  DHCP_FQDN now allows user to specify fully qualified domain name to be
  sent to DHCP server instead of just using simple hostname. This option
  takes precedence before DHCP_HOSTNAME variable.

  DHCP_SEND_HOSTNAME can be used to tell initscripts to not send either
  DHCP_HOSTNAME or DHCP_FQDN to DHCP server.

  Both of these options should behave same as they do in NetworkManager.

  This commit contains a lot of whitespace changes.
  Use 'git diff --ignore-all-space' to display the relevant changes.