You can't kill the adb server from Eclipse, simply because that feature has not been implemented in Eclipse ADT plugin.
This is from Android Official documentation on Eclipse ADT plugin:
adb: Provides access to a device from your development system. Some features of adb are integrated into ADT such as project installation (Eclipse run menu), file transfer, device enumeration, and logcat (DDMS). You must access the more advanced features of adb, such as shell commands, from the command line.