Spawn isolated processes for the lmkd kill test

In case the individual process is running out of address space,
we could spawn isolated processes to fill up the system memory.

Bug: 159051024
Test: atest \
      CtsAppExitTestCases:ActivityManagerAppExitInfoTest#testLmkdKill
Change-Id: Ibf2b98a9cbfed1e138b5e3576bb37aa3f5197f0d
Merged-In: Ibf2b98a9cbfed1e138b5e3576bb37aa3f5197f0d
3 files changed