This is the same problem as a number of other have reported, e.g.
Failed to fetch URL https://dl-ssl.google.com/android/repository/addons_list-1.xml, reason: Connect
I have faced the same problem in Windows. Then it worked for me after doing the following steps:
Open cmd as administrator
ping dl-ssl.google.com
Go to the SDk manager and retry the installation
(Note: Make sure to have the default options in SDK manager. Dont check Force https.... option before following the above steps)