rpm and deb tasks incorrectly set the SGID permission

[Zuplyx]

#429 introduced the Boolean property setgid for explicitly setting the SGID permission.
But in the rpm and deb CopyActions setgid is mistakenly evaluated as a String. Since in Groovy any non-empty String is coerced to true, this leads to the SGID being set even if setgid = false.

Currently the only way to not set the SGID is to set setgid = null.

Impacted Code:

gradle-ospackage-plugin/src/main/groovy/com/netflix/gradle/plugins/deb/DebCopyAction.groovy

Lines 138 to 143 in c915fd6

	String setgid = lookup(specToLookAt, 'setgid') ?: task.setgid
	int fileMode = dirDetails.mode
	if (setgid) {
	fileMode = fileMode | 02000
	}

gradle-ospackage-plugin/src/main/groovy/com/netflix/gradle/plugins/rpm/RpmCopyAction.groovy

Lines 189 to 192 in c915fd6

	String setgid = lookup(specToLookAt, 'setgid') ?: task.setgid
	if (setgid) {
	dirMode = dirMode | 02000
	}