Fix ARTBootASLRTest.java

Original test was incorrect since there is some mapping info at the
start of the lines of the form:
"7cc6c59000-7cc6c8d000 rw-p 00000000 00:00 0 "

Removed system image test since the bitmap will cause a mapping there.

Bug: 143372803
Test: atest ARTBootASLRTest.java

Change-Id: Ib0a7fe27743b312382f1618029097334505e0621