Comment 0 for bug 1896448

Issue found on 5.4.0-1025.25~18.04.1, this issue was not spotted before fixing the false-negative return value of this rtnetlink.sh test (bug 1890136)

 # Usage: ... { ip6gre | ip6gretap | ip6erspan} [ remote ADDR ]
 # [ local ADDR ]
 # [ [i|o]seq ]
 # [ [i|o]key KEY ]
 # [ [i|o]csum ]
 # [ hoplimit TTL ]
 # [ encaplimit ELIM ]
 # [ tclass TCLASS ]
 # [ flowlabel FLOWLABEL ]
 # [ dscp inherit ]
 # [ fwmark MARK ]
 # [ dev PHYS_DEV ]
 # [ noencap ]
 # [ encap { fou | gue | none } ]
 # [ encap-sport PORT ]
 # [ encap-dport PORT ]
 # [ [no]encap-csum ]
 # [ [no]encap-csum6 ]
 # [ [no]encap-remcsum ]
 # [ erspan IDX ]
 #
 # Where: ADDR := IPV6_ADDRESS
 # TTL := { 0..255 } (default=64)
 # KEY := { DOTTED_QUAD | NUMBER }
 # ELIM := { none | 0..255 }(default=4)
 # TCLASS := { 0x0..0xff | inherit }
 # FLOWLABEL := { 0x0..0xfffff | inherit }
 # MARK := { 0x0..0xffffffff | inherit }
 # Cannot find device "ip6gretap00"
 # FAIL: ip6gretap