Revert "[findBugs] Silence DM_STRING_CTOR on PacketLineIn"

This reverts commit 1e510ec20e0391010419b17e9a9095ad54941d3c.

Instead work around the warning by defining our constant by
constructing it through a StringBuilder.

Change-Id: If139509e769d649609c62eff359ebaea5dd286b2
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
CC: Matthias Sohn <matthias.sohn@sap.com>
CC: Chris Aniszczyk <caniszczyk@gmail.com>