gdb_server: remove call to jtag_execute_queue()

gdb_server: remove call to jtag_execute_queue()

In the initial commit 6c9b804d6187edda4f46f8458deec0b17ec76bb9
in 2007's svn://svn.berlios.de/openocd/trunk@246
a target script gdb_program_config was called before gdb flash
programming. To guarantee the script does not left any pending
command in the jtag queue, a call to jtag_execute_queue() was
inserted after the execution of the script.

In following commit ef1cfb23947bd32798077c6abb5c25a049460ae9
in 2008's svn://svn.berlios.de/openocd/trunk@975
the script was replaced by the event "old-gdb_program_config" and
the call to jtag_execute_queue() get executed in every case, even
if the event handler was not present.

At last, commit bb3793c9a4ccd232c4ee3ce0a36bf200589ca0bb
("target: remove legacy target events") stripped away the
obsolete event but left the call to jtag_execute_queue(), now
completely useless.

Remove the call to jtag_execute_queue() and clean-up the code
around it.

Change-Id: I284f54d656d431ad6cdc25ca18218c09db31bd25
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/4911
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>