releng: Change the "-Pbuild-rcp" directive to a "-Dskip-rcp" property

releng: Change the "-Pbuild-rcp" directive to a "-Dskip-rcp" property

<activeByDefault>true</activeByDefault> is very bad and
should not be used. Among other things, it effectively prevents
from defining more than one profile in a given pom.xml.

Change-Id: Id30897025a7df37d14014ef605122416e0b33dc7
Signed-off-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Reviewed-on: https://git.eclipse.org/r/83402
Reviewed-by: Hudson CI
Reviewed-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Tested-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>