Added the Key Pair drop down list to UI forms

Added new parameter for each Linux-based
(Linux Telnet and Linux Apache) services.

User can select the Key Pair from the drop down list
durring the Murano Linux-based services configuration.

Implemented: blueprint key-pair-for-linux-services
Change-Id: I774cd3714791ea7db1bd4889d38f52a1067c50fa