Create directory when no LaunchAgents directory doens't exist

[tbille]

When running the python install script on MacOs if the LaunchAgents doesn't exists yet the script fails.

https://github.com/ilyatbn/aws_alwayson/blob/master/aosvc-python/install_mac.sh#L4

➜  aosvc-python git:(master) ./install_mac.sh 
+ launch_config_dir=/Users/toto/Library/LaunchAgents
+ launch_config_path=/Users/toto/Library/LaunchAgents/com.github.ilyatbn.aws_alwayson.plist
+ service_path=/Users/toto/.local/share/aosvc/bin
++ id -u
+ user_uid=502
+ mkdir -p /Users/toto/.local/share/aosvc/bin
+ cp aosvc /Users/toto/.local/share/aosvc/bin
+ cp aosvc.plist /Users/toto/Library/LaunchAgents/com.github.ilyatbn.aws_alwayson.plist
cp: /Users/toto/Library/LaunchAgents/com.github.ilyatbn.aws_alwayson.plist: No such file or directory

The current fix is to manually create the directory and re-run the script.