RFR 8098854: Do cleanup in a proper order in mscapi

[Ivan Gerasimov]

Hello everyone!

The changeset consists of two parts:
- checking systematically for NULL result of FindClass() and GetMethodID(),
- calling CryptReleaseContext() after CryptDestroyHash(), as it is 
suggested in MSDN [1].

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8098854
WEBREV: http://cr.openjdk.java.net/~igerasim/8098854/00/webrev/

[1] 
https://msdn.microsoft.com/en-us/library/windows/desktop/aa380268(v=vs.85).aspx

Sincerely yours,
Ivan