Lock buffer before printing package name

String8's buffer is not when calling String8.string() function,
and can change if the reference returned by String8.string is kept past
one access. Repeated reads to the reference returned by String8.string()
can lead to garbage values.

This CL locks the buffer of a packageName's String8 object before using
it for printing.

Bug: 199746421
Test: Manually Tested
Change-Id: Ib237f078f2b4b9254208477a56db7a2921d72185