webappmanager: Add dependency on serviceinstaller

Compilation fails otherwise:

| /home/morphis/data/oe/webos-ports-setup/webos-ports/tmp-eglibc/sysroots/
  x86_64-linux/usr/libexec/armv7a-vfp-neon-webos-linux-gnueabi/gcc/arm-webos-linux-gnueabi/4.7.2/ld:
cannot find -lserviceinstaller
| collect2: error: ld returned 1 exit status

Open-webOS-DCO-1.0-Signed-off-by: Simon Busch <morphis@gravedo.de>
Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@palm.com>
Change-Id: I893ad039f71ed384e17a3d2fd6540335b5c785cb
Reviewed-on: http://g2g.palm.com/1275
Reviewed-by: Martin Jansa <martin.jansa@palm.com>
Tested-by: Martin Jansa <martin.jansa@palm.com>
Reviewed-by: Build Verification
Reviewed-by: Susan Montooth <susan.montooth@palm.com>