nftables: Fix missing leading whitespace with ':append'

Mitigate occurence where ':append' operator is used and leading
whitespace character is obviously missing, risking inadvertent
string concatenation.

Signed-off-by: Niko Mauno <niko.mauno@vaisala.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
(cherry picked from commit d259672)
Signed-off-by: Niko Mauno <niko.mauno@vaisala.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>

meta-networking/recipes-filter/nftables/nftables_1.0.2.bb

@@ -38,7 +38,7 @@ RDEPENDS:${PN}-ptest += " make bash python3-core python3-ctypes python3-json pyt
 
 TESTDIR = "tests"
 
-PRIVATE_LIBS:${PN}-ptest:append = "libnftables.so.1"
+PRIVATE_LIBS:${PN}-ptest:append = " libnftables.so.1"
 
 do_install_ptest() {
     cp -rf ${S}/build-aux ${D}${PTEST_PATH}