ash: respect -p flag when command builtin is run with -v/-V

ash: respect -p flag when command builtin is run with -v/-V

The command builtin should only check the default path, not $PATH,
when the -p flag is used along with -v/-V.

Based on commits 65ae84b (by Harald van Dijk) and 29ee27d (by Herbert
Xu) from git://git.kernel.org/pub/scm/utils/dash/dash.git).

function                                             old     new   delta
commandcmd                                            72      87     +15
describe_command                                     437     450     +13
typecmd                                               84      86      +2
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(add/remove: 0/0 grow/shrink: 3/0 up/down: 30/0)               Total: 30 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>