Relax SharedLogTest asserts

This patch makes the asserts of SharedLogTest looser so that it is less
likely to get invalidated by a date formatting change.

The timestamp format of LocalLog changed in commit 6229d990 from
"mm-dd HH:MM:SS.xxx" to "yyy-mm-ddTHH:MM:SS.xxx".

Bug: 62918393
Test: runtest frameworks-net pass
Change-Id: I57ab3e05a0f3093f9c7b1760e596a3919d4f2ed7