browser-android: Use execv() directly instead of os_exec()

browser-android: Use execv() directly instead of os_exec()

This allows the URL to be passed as a single argument to the program
instead of getting split into multiple by os_exec(). This makes the
operation more robust for cases where the URL could have been received
from an external source and could potentially add extra arguments to the
command line.

In addition, fix the /system/bin/input execution by using system() for
it instead of execv() through os_exec(). /system/bin/input is a script
that execv() won't be able to run. Since the full command line is
specified, system() can be used for this. The keycode is also changed
from 3 to KEYCODE_HOME to make this work with current Android version.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>