Fix libxbps/update_shlibs:shlib_bump_revdep_diff test.

How to reproduce it:

	- A-1.0_1 provides liba.so.1
	- B-1.0_1 provides libb.so.1
	- C-1.0_1 requires liba.so.1 and libb.so.1
	- A-2.0_1 provides liba.so.2
	- C-2.0_1 required liba.so.2

This test case failed because it was checking the required shared libraries
from current installed package, rather than the updated pkg in transaction.