[11u] RFR 8224589: Improve startup behavior of SecurityProperties

[Martin Balao]

Please note that some bits of 8224589 were backported to jdk11u in
8215032 [1]. In particular, "privilegedGetOverridable" and
"getOverridableProperty" functions were placed in
SecurityProperties.java [2]. I suggest to take those bits from the
8215032 backport, so these common functions can be shared between
different classes.

8215032 is waiting for a review and won't make it for 2019-10 CPU.

Thanks,
Martin.-

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[1] -
http://mail.openjdk.java.net/pipermail/jdk-updates-dev/2019-August/001712.html
[2] -
http://cr.openjdk.java.net/~mbalao/webrevs/8215032/8215032.webrev.jdk11u.00/raw_files/new/src/java.base/share/classes/sun/security/util/SecurityProperties.java