servicemanager: Allow '/' character in service names.

To work as instance name separater consistently w/ HIDL.

In HIDL, people are used to writing something like:
    android.hardware.light@2.0::ILight/default

In AIDL, the same thing would look like:
    android.hardware.light.ILight/default

Bug: 136027762
Test: use '/' in service name
Change-Id: Ie108029bd37b09647b761c5c5ce3a901dbfd4f19