virt-admin: Tweak command parsing logic so that aliases point to new commands

Change the logic in a way, so that VSH_CMD_FLAG_ALIAS behaves similarly to
how VSH_OT_ALIAS for command options, i.e. there is no need for code duplication
for the alias and the aliased command structures. Along with that change,
switch any existing VSH_CMD_FLAG_ALIAS occurrences to this new format. Also,
since this patch introduces a new command structure element, adjust the
virsh-self-test test to make sure we won't ever miss to specify the '.alias'
member for an aliased command because doing that would lead to an internal
error.

Signed-off-by: Erik Skultety <eskultet@redhat.com>

tools/vsh.h

@@ -179,6 +179,7 @@ struct _vshCmdDef {
     const vshCmdOptDef *opts;   /* definition of command options */
     const vshCmdInfo *info;     /* details about command */
     unsigned int flags;         /* bitwise OR of VSH_CMD_FLAG */
+    const char *alias;          /* name of the aliased command */
 };
 
 /*
@@ -445,7 +446,8 @@ bool cmdSelfTest(vshControl *ctl, const vshCmd *cmd);
         .handler = cmdSelfTest,                         \
         .opts = NULL,                                   \
         .info = info_selftest,                          \
-        .flags = VSH_CMD_FLAG_NOCONNECT | VSH_CMD_FLAG_ALIAS    \
+        .flags = VSH_CMD_FLAG_NOCONNECT | VSH_CMD_FLAG_ALIAS,    \
+        .alias = "self-test"                            \
     }