Fix the issue provider can be wrong when requesting slice permission

SlicePermissionActivity reads provider_pkg from intent, which can be
modified at will. As a result user might see incorrect package name in
the dialog granting slice permission.

Bug: 159145361
Test: manual
Merged-In: I8b66c02786df4096dad74b7e76255d5ddd1d609d
Change-Id: I8b66c02786df4096dad74b7e76255d5ddd1d609d
(cherry picked from commit 0ad32a2d70ae410a59d730802b47af7c27b0b4a3)