init: Add support "&&" operator in property triggers

"&&" operator can now be used to test the validity
of two of more properties.

For example:

on property:test.a=1 && property:test.b=1
    setprop test.c 1

The above stub sets the test.c to 1 only when
both test.a=1 and test.b=1

Change-Id: I72c19f7aa92231372a416193618ee6c7fd368141
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>