asterisk: Fix extension's type detection
It occured that string comparison with newer version of busybox v1.34.1 is not working properly in config_asterisk.sh script. Change the method of string comparison to be POSIX compliant fixes the issue.
It occured that string comparison with newer version of busybox v1.34.1 is not working properly in config_asterisk.sh script. Change the method of string comparison to be POSIX compliant fixes the issue.