install: add insecure cipher options for older devices/firmwares

Requires explicit choice via flag

fixes: https://github.com/gregtwallace/apc-p15-tool/issues/1

pkg/app/config.go

@@ -32,10 +32,11 @@ type config struct {
 	}
 	install struct {
 		keyCertPemCfg
-		hostAndPort *string
-		fingerprint *string
-		username    *string
-		password    *string
+		hostAndPort    *string
+		fingerprint    *string
+		username       *string
+		password       *string
+		insecureCipher *bool
 	}
 }
 
@@ -92,6 +93,7 @@ func (app *app) getConfig(args []string) error {
 	cfg.install.fingerprint = installFlags.StringLong("fingerprint", "", "the SHA256 fingerprint value of the ups' ssh server")
 	cfg.install.username = installFlags.StringLong("username", "", "username to login to the apc ups")
 	cfg.install.password = installFlags.StringLong("password", "", "password to login to the apc ups")
+	cfg.install.insecureCipher = installFlags.BoolLong("insecurecipher", "allows the use of insecure ssh ciphers (NOT recommended)")
 
 	installCmd := &ff.Command{
 		Name:      "install",