RFR: 8359163: Fix path to current module on ios

[Johan Vos]

Minimize ios-specific logic to calculate the location for java_home.
The java_home property should be based on the jvm_path, and not on the user_home

Fix JDK-8359163

This patch still has ios-specific logic, e.g. we don't have a {client/server} suffix to the jvm home. More important, though, is that we do not want to point to userspace for the location of the jvm modules etc itself. Those should be derived from the installed application location, which matches the jvm_home property.
Applying this patch removes one more location where the mobile repository differs from upstream jdk.

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Commit messages:
 - Minimize ios-specific logic to calculate the location for java_home.

Changes: https://git.openjdk.org/mobile/pull/39/files
  Webrev: https://webrevs.openjdk.org/?repo=mobile&pr=39&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8359163
  Stats: 7 lines in 1 file changed: 1 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/mobile/pull/39.diff
  Fetch: git fetch https://git.openjdk.org/mobile.git pull/39/head:pull/39

PR: https://git.openjdk.org/mobile/pull/39