NotificationManager : Fix security exception

If the call is from a user process, using USER_CURRENT_OR_SELF avoids a security
exception in such cases.

Change-Id: I2f25917ecfabc80d3a193d63020ad11480edf8ec
Merge branch 'cm-10.1' of https://github.com/CyanogenMod/android_frameworks_base into linaro