Merge from widevine repo of http://go/wvgerrit/14870
OEMCrypto_GetMaxNumberOfSessions is not required to return a hard
limit for the number of sessions. This CL adjusts the test to verify
we can open within 5% of the maximum number of sessions.
bug: 22029687
Change-Id: I6e72e39338cead8d547cdb194a32fb7e7dc53037