[M120 Migration][VD] Increase buffer size of cmd line for child process

[M120 Migration][VD] Increase buffer size of cmd line for child process

On TV product, kdbus connecting was failed because saved size of command
line in kernel and actual size were different. So we need to increase
buffer size of command line when zygote process is executed by execvp().
This patch appends dummy argument once calling execvp().

Reference:
  - https://review.tizen.org/gerrit/#/c/291592/

Change-Id: I9da3f12b2a464c2598012541f720fa0ff15a043b
Signed-off-by: jie <jie137.zhang@samsung.com>
(cherry picked from commit d33bf9d2b81e6040f60f7789c40fa41cdc660531)