GDB: No longer synchronize on a string.

GDB: No longer synchronize on a string.

This is dangerous for two reasons:
1- if the string value changes, the object changes too, so we can
corrupt data.
2- if the string is internalized, it can cause unwanted delays with
other objects synchronizing coincidentally on the same string.

Change-Id: Ibfeb3702ef82424b2fca86956f8227b52ae8b945
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/56133
Reviewed-by: Hudson CI
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>