ril: Ignore unsupported IMS state request

These requests are left dangling, return an explicit not-supported
reply to avoid timeouts

Change-Id: I5ddecf43e112c64ea719c5b753993b5b8f0d5dde
Merge branch 'cm-11.0' of github.com:CyanogenMod/android_device_lge_g2-common into cm-11.0