Do not check router's permission on requests from MediaRouter2Manager

In order to allow getting the session creation requests from
MediaRouter2Manager, this CL moves the permission check to inside
requestCreateSessionWithRouter2Locked().

Bug: 153811416
Test: Builds successfully
Change-Id: Ief4b7f4bb73404bcf81427d19e3a753c7d78ec5b
1 file changed