RDKCOM-926 RDKCMF-8515: WebGUI was not accessible sometime
RDKCOM-926 RDKCMF-8515: WebGUI was not accessible sometime

Reason for change: WebGUI was not accessible as lighttpd was not running sometime.
There was a race condition to execute webgui.sh. Two CCSP processes were trying to execute webgui.sh
at the sometime, but both the instances were getting struck in a loop
in webgui.sh and exiting before running lighttpd binary.
Synchronization logic has been added in webgui.sh so that only single process can execute webgui.sh at a time.
Test Procedure:
1) Reboot the CM
2) WebGUI should be accessible every time
3) Repeat the test for 20-25 times
Risk: None
Risks: Low.
Signed-off-by: Stephen Barrett <stephen.barrett@accenture.com>

(cherry picked from commit dc220b815b7b16bc58e21538867abdce758a4bab)

Change-Id: I4f29ae09684846ce20b71390e465f2ca9e13a9da

rdkcmf/rdkb-webui,rdkcmf/rdkb-webui,rdkcmf/rdkb-webui,rdkcmf/rdkb-webui,rdkcmf/rdkb-webui